Performance of serum C-reactive protein as a screening test for smear-negative tuberculosis in an ambulatory high HIV prevalence population

Host blood protein biomarkers to screen for tuberculosis disease: a systematic review and meta-analysis

Non-sputum tests are needed to improve tuberculosis (TB) diagnosis and close the diagnostic gap. The World Health Organization's target product profile (TPP) for point-of-care (POC) screening tests requires a minimum sensitivity of 90% and a specificity of 70%. Our objective was to identify host blood protein biomarkers meeting TPP criteria. A systematic review was conducted and reported following PRISMA guidelines. Data extraction and quality assessment with Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) were completed for the included studies. Heterogeneity was assessed. For biomarkers reporting sensitivity and specificity in at least four studies, a random-effects meta-analysis was performed for biomarkers with similar cut-offs. We screened 4,651 citations and included 65 studies that enrolled 16,010 participants and evaluated 156 host proteins. Most (47/65) studies enrolled adult pulmonary TB (PTB), with 15 studies in adult extra-pulmonary TB and 5 in children. Small early-stage discovery studies with case-control design were common (24/65) and had a high risk of bias. For adult PTB, CRP, IP-10, NCAM-1, and SAA met TPP criteria in high-quality studies. There was a high degree of heterogeneity in biomarker cut-offs and study design. CRP at 10 mg/L cut-off was meta-analyzed from 10 studies; pooled sensitivity 86% [95% confidence interval (CI): 80-95] and pooled specificity 67% (95% CI: 54-79). In people living with HIV (six studies), CRP pooled sensitivity was 93% (95% CI: 90-95), and pooled specificity was 59% (95% CI: 40-78). We identified promising biomarkers that performed well in high-quality studies. Data overall are limited and highly heterogenous. Further standardized validation across subgroups in prospective studies is needed before translating into POC assays.

IMPORTANCE

To our knowledge, this is the first comprehensive systematic review of host blood protein biomarkers for tuberculosis (TB), and we identified promising biomarkers for a TB screening test.

Bad company? The pericardium microbiome in people investigated for tuberculosis pericarditis in an HIV-prevalent setting

Background

The microbiome likely plays a role in tuberculosis (TB) pathogenesis. We evaluated the site-of-disease microbiome and predicted metagenome in people with presumptive tuberculous pericarditis, a major cause of mortality, and explored for the first time, the interaction between its association with C-reactive protein (CRP), a potential diagnostic biomarker and the site-of-disease microbiome in extrapulmonary TB.

Methods

People with effusions requiring diagnostic pericardiocentesis (n=139) provided background sampling controls and pericardial fluid (PF) for 16S rRNA gene sequencing analysed using QIIME2 and PICRUSt2. Blood was collected to measure CRP.

Results

PF from people with definite (dTB, n=91), probable (pTB, n=25), and non- (nTB, n=23) tuberculous pericarditis differed in β-diversity. dTBs were, vs. nTBs, Mycobacterium-, Lacticigenium-, and Kocuria- enriched. Within dTBs, HIV-positives were Mycobacterium-, Bifidobacterium- , Methylobacterium- , and Leptothrix -enriched vs. HIV-negatives and HIV-positive dTBs on ART were Mycobacterium - and Bifidobacterium -depleted vs. those not on ART. Compared to nTBs, dTBs exhibited short-chain fatty acid (SCFA) and mycobacterial metabolism microbial pathway enrichment. People with additional non-pericardial involvement had differentially PF taxa (e.g., Mycobacterium -enrichment and Streptococcus -depletion associated with pulmonary infiltrates). Mycobacterium reads were in 34% (31/91), 8% (2/25) and 17% (4/23) of dTBs, pTBs, and nTBs, respectively. β-diversity differed between patients with CRP above vs. below the median value ( Pseudomonas -depleted). There was no correlation between enriched taxa in dTBs and CRP.

Conclusions

PF is compositionally distinct based on TB status, HIV (and ART) status and dTBs are enriched in SCFA-associated taxa. The clinical significance of these findings, including mycobacterial reads in nTBs and pTBs, requires evaluation.

C-reactive protein and procalcitonin use in adults in low- and middle-income countries: a narrative review

Objectives

C-reactive protein (CRP) and procalcitonin (PCT) are widely used biomarkers in high-income countries. However, evidence for their use in low- and middle-income countries (LMICs) is scant. Because many factors, including rates of endemic disease, comorbidities and genetics, may influence biomarkers' behaviour, we aimed to review available evidence generated in LMICs.

Methods

We searched the PubMed database for relevant studies within the last 20 years that originated in regions of interest (Africa, Latin America, Middle East, South Asia or South East Asia), and full-text articles involving diagnosis, prognostication and evaluation of therapeutic response with CRP and/or PCT in adults (n = 88) were reviewed and categorized in 12 predefined focus areas.

Results

Overall, results were highly heterogeneous, at times conflicting, and often lacking clinically useful cut-off values. However, most studies demonstrated higher levels of CRP/PCT in patients with bacterial versus other infections. HIV and TB patients had consistently higher levels of CRP/PCT versus controls. In addition, higher CRP/PCT levels at baseline and follow-up in HIV, TB, sepsis and respiratory tract infections were associated with poorer prognosis.

Conclusions

Evidence generated from LMIC cohorts suggests that CRP and PCT may have potential to become effective clinical guiding tools particularly in respiratory tract infections, sepsis and HIV/TB. However, more studies are needed to define potential scenarios for use and cost-effectiveness. Consensus across stakeholders regarding target conditions, laboratory standards and cut-off values would support the quality and applicability of future evidence.

Use of point-of-care C-reactive protein testing for screening of tuberculosis in the community in high-burden settings: a prospective, cross-sectional study in Zambia and South Africa

BACKGROUND

WHO recommends community-wide, systematic tuberculosis screening in high-prevalence settings. C-reactive protein has been proposed as a tuberculosis screening tool for people living with HIV. We aimed to assess the performance of a point-of-care C-reactive protein test for tuberculosis screening in the community in two countries with a high tuberculosis burden.

METHODS

We conducted a prospective, cross-sectional study in four communities in Zambia and South Africa, nested in a tuberculosis prevalence survey. We included adults (aged ≥15 years) who were sputum-eligible (tuberculosis-suggestive symptoms or computer-aided-detection score ≥40 on chest x-ray) and whose sputum was tested with Xpert Ultra and liquid culture. A 5% random sample of individuals who were non-sputum-eligible was also included. We calculated sensitivity and specificity of point-of-care C-reactive protein testing, alone and combined with symptom screening, to detect tuberculosis in participants who were sputum-eligible, compared with a microbiological reference standard (positive result in Xpert Ultra, culture, or both).

FINDINGS

Between Feb 19 and Aug 11, 2019, 9588 participants were enrolled in the tuberculosis prevalence study, 1588 of whom had C-reactive protein testing and received results (875 [55·1%] were women and girls, 713 [44·9%] were men and boys, 1317 [82·9%] were sputum-eligible, and 271 [17·1%] were non-sputum-eligible). Among participants who were sputum-eligible, we identified 76 individuals with tuberculosis, of whom 25 were living with HIV. Sensitivity of point-of-care C-reactive protein testing with a cutoff point of 5 mg/L or more was 50·0% (38/76, 95% CI 38·3-61·7) and specificity was 72·3% (890/1231, 69·7-74·8). Point-of-care C-reactive protein combined in parallel with symptom screening had higher sensitivity than symptom screening alone (60·5% [46/76, 95% CI 48·6-71·6] vs 34·2% [26/76, 23·7-46·0]). Specificity of point-of-care C-reactive protein combined in parallel with symptom screening was 51·7% (636/1231, 95% CI 48·8-54·5) versus 70·5% (868/1231, 67·9-73·0) with symptom screening alone. Similarly, in people living with HIV, sensitivity of point-of-care C-reactive protein combined with symptom screening was 72·0% (18/25, 95% CI 50·6-87·9) and that of symptom screening alone was 36·0% (9/25, 18·0-57·5). Specificity of point-of-care C-reactive protein testing combined in parallel with symptom screening in people living with HIV was 47·0% (118/251, 95% CI 40·7-53·4) versus 72·1% (181/251, 66·1-77·6) with symptom screening alone.

INTERPRETATION

Point-of-care C-reactive protein testing alone does not meet the 90% sensitivity stipulated by WHO's target product profile for desirable characteristics for screening tests for detecting tuberculosis. However, combined with symptom screening, it might improve identification of individuals with tuberculosis in communities with high prevalence, and might be particularly useful where other recommended tools, such as chest x-ray, might not be readily available.

FUNDING

European and Developing Countries Clinical Trials Partnership.

Sensitivity and specificity of CRP and symptom screening as tuberculosis screening tools among HIV-positive and negative outpatients at a primary healthcare facility in Lusaka, Zambia: a prospective cross-sectional study

OBJECTIVES

To evaluate the performance of point-of-care C-reactive protein (CRP) as a screening tool for tuberculosis (TB) using a threshold of 10 mg/L in both people living with HIV (PLHIV) and HIV-negative individuals and compare it to symptom screening using a composite reference for bacteriological confirmation of TB.

METHODS

Prospective cross-sectional study.

SETTING

A primary healthcare facility in Lusaka, Zambia.

PARTICIPANTS

Consecutive adults (≥18 years) presenting for routine outpatient healthcare were enrolled. Of the 816 individuals approached to participate in the study, 804 eligible consenting adults were enrolled into the study, of which 783 were included in the analysis.

PRIMARY OUTCOME MEASURES

Sensitivity, specificity, positive predictive value and negative predictive value (NPV) of CRP and symptom screening.

RESULTS

Overall, sensitivity of WHO-recommended four-symptom screen (W4SS) and CRP were 87.2% (80.0-92.5) and 86.6% (79.6-91.8) while specificity was 30.3% (26.7-34.1) and 34.8% (31.2-38.6), respectively. Among PLHIV, sensitivity of W4SS and CRP was 92.2% (81.1-97.8) and 94.8% (85.6-98.9) while specificity was 37.0% (31.3-43.0) and 27.5% (22.4-33.1), respectively. Among those with CD4≥350, the NPV for CRP was 100% (92.9-100). In the HIV negative, sensitivity of W4SS and CRP was 83.8% (73.4-91.3) and 80.3% (69.5-88.5) while specificity was 25.4% (20.9-30.2) and 40.5% (35.3-45.6), respectively. Parallel use of CRP and W4SS yielded a sensitivity and NPV of 100% (93.8-100) and 100% (91.6-100) among PLHIV and 93.3% (85.1-97.8) and 90.0% (78.2-96.7) among the HIV negatives, respectively.

CONCLUSION

Sensitivity and specificity of CRP were similar to symptom screening in HIV-positive outpatients. Independent use of CRP offered limited additional benefit in the HIV negative. CRP can independently accurately rule out TB in PLHIV with CD4≥350. Parallel use of CRP and W4SS improves sensitivity irrespective of HIV status and can accurately rule out TB in PLHIV, irrespective of CD4 count.

Analytical performance of 17 commercially available point-of-care tests for CRP to support patient management at lower levels of the health system

Accurate and precise point-of-care (POC) testing for C-reactive protein (CRP) can help support healthcare providers in the clinical management of patients. Here, we compared the analytical performance of 17 commercially available POC CRP tests to enable more decentralized use of the tool. The following CRP tests were evaluated. Eight quantitative tests: QuikRead go (Aidian), INCLIX (Sugentech), Spinit (Biosurfit), LS4000 (Lansionbio), GS 1200 (Gensure Biotech), Standard F200 (SD Biosensor), Epithod 616 (DxGen), IFP-3000 (Xincheng Biological); and nine semi-quantitative tests: Actim CRP (ACTIM), NADAL Dipstick (nal von minden), NADAL cassette (nal von minden), ALLTEST Dipstick (Hangzhou Alltest Biotech), ALLTEST Cassette cut-off 10-40-80 (Hangzhou Alltest Biotech), ALLTEST Cassette cut-off 10-30 (Hangzhou Alltest Biotech), Biotest (Hangzhou Biotest Biotech), BTNX Quad Line (BTNX), BTNX Tri Line (BTNX). Stored samples (n = 660) had previously been tested for CRP using Cobas 8000 Modular analyzer (Roche Diagnostics International AG, Rotkreuz, Switzerland (reference standards). CRP values represented the clinically relevant range (10-100 mg/L) and were grouped into four categories (<10 mg/L, 10-40 mg/L or 10-30 mg/L, 40-80 mg/L or 30-80 mg/L, and > 80mg/L) for majority of the semi-quantitative tests. Among the eight quantitative POC tests evaluated, QuikRead go and Spinit exhibited better agreement with the reference method, showing slopes of 0.963 and 0.921, respectively. Semi-quantitative tests with the four categories showed a poor percentage agreement for the intermediate categories and higher percentage agreement for the lower and upper limit categories. Analytical performance varied considerably for the semi-quantitative tests, especially among the different categories of CRP values. Our findings suggest that quantitative tests might represent the best choice for a variety of use cases, as they can be used across a broad range of CRP categories.

Clinical utility of C-reactive protein-based triage for presumptive pulmonary tuberculosis in South African adults

BACKGROUND

Identification of an accurate, low-cost triage test for pulmonary TB among people presenting to healthcare facilities is an urgent global research priority. We assessed the diagnostic accuracy and clinical utility of C-reactive protein (CRP) for TB triage among symptomatic adult outpatients, irrespective of HIV status.

METHODS

We prospectively enrolled adults reporting at least one (for people with HIV) or two (for people without HIV) symptoms of cough, fever, night sweats, or weight loss at two TB clinics in Cape Town, South Africa. Participants provided sputum for culture and Xpert MTB/RIF Ultra. We evaluated the diagnostic accuracy of CRP (measured using a laboratory-based assay) against a TB-culture reference standard as the area under the receiver operating characteristic curve (AUROC), and sensitivity and specificity at pre-specified thresholds. We assessed clinical utility using decision curve analysis and benchmarked against WHO recommendations.

RESULTS

Of 932 included individuals, 255 (27%) had culture-confirmed pulmonary TB and 389 (42%) were living with HIV. CRP demonstrated an AUROC of 0·80 (95% confidence interval 0·77-0·83), with sensitivity 93% (89-95%) and specificity 54% (50-58%) using a primary cut-off of ≥10 mg/L. Performance was similar among people with HIV to those without. In decision curve analysis, CRP-based triage offered greater clinical utility than confirmatory testing for all up to a number willing to test threshold of 20 confirmatory tests per true positive pulmonary TB case diagnosed (threshold probability 5%). If it is possible to perform more confirmatory tests than this, a 'confirmatory test for all' strategy performed better.

CONCLUSIONS

CRP achieved the WHO-defined sensitivity, but not specificity, targets for a triage test for pulmonary TB and showed evidence of clinical utility among symptomatic outpatients, irrespective of HIV status.

FUNDING

South African Medical Research Council, EDCTP2, Royal Society Newton Advanced Fellowship, Wellcome Trust, National Institute of Health Research, Royal College of Physicians.

Screening performance of C-reactive protein for active pulmonary tuberculosis in HIV-positive patients: A systematic review with a meta-analysis

Background

Tuberculosis (TB) is the leading infectious cause of mortality worldwide. In the last years, resistant strains of the etiological agent, Mycobacterium tuberculosis, have emerged, thus demanding more triage tests to identify active pulmonary TB (PTB) patients and to evaluate their disease severity. Therefore, acute-phase reaction serum tests are required for monitoring TB patients, among WHO symptom screening recommendations. C-reactive protein (CRP) is a non-specific inflammatory biomarker that has been recently proposed for TB screening and can be quantitatively analyzed through cost-effective point-of-care assays. A previous meta-analysis found CRP to be highly sensitive and moderately specific for active PTB with confirmed HIV infection.

Methods

We performed a meta-analysis update of diagnostic tests, pooling sensitivities, and specificities in order to assess the accuracy of CRP as a potential test for the screening of HIV-associated PTB in outpatients. We searched MEDLINE, Web of Science, and SCOPUS for eligible articles before 19 October 2021.

Results

We identified 13 eligible studies with HIV-positive patients with PTB. At a CRP threshold of 10 mg/L, CRP pooled sensitivity was 87% (76%–93%) and pooled specificity was 67% (49%–81%), with an area under the curve (AUC) of 0.858. Using a CRP threshold of 8 mg/L, pooled sensitivity was 82% (72%–89%) and pooled specificity was 82% (67%–92%), with an AUC of 0.879. We found that CRP has a high sensitivity in the screening of PTB in HIV-positive outpatients, consistent with findings reported previously.

Conclusions

Regardless of pooled specificity, better results were found using the CRP threshold of 8 mg/L as a test screening of PTB, meeting the need of further approaching specific TB diagnostic methods and reducing resource consumption.

The Role of C-Reactive Protein as a Triage Tool for Pulmonary Tuberculosis in Children

BACKGROUND

C-reactive protein (CRP) has shown promise as a triage tool for pulmonary tuberculosis (TB) in adults living with the human immunodeficiency virus. We performed the first assessment of CRP for TB triage in children.

METHODS

Symptomatic children less than 15 years old were prospectively enrolled in Kampala, Uganda. We completed a standard TB evaluation and measured CRP using a point-of-care assay. We determined the sensitivity and specificity of CRP to identify pulmonary TB in children using 10 mg/L and 5 mg/L cut-off points and generated a receiver operating characteristic (ROC) curve to determine alternative cut-offs that could approach the target accuracy for a triage test (≥90% sensitivity and ≥70% specificity).

RESULTS

We included 332 children (median age 3 years old, interquartile range [IQR]: 1-6). The median CRP level was low at 3.0 mg/L (IQR: 2.5-26.6) but was higher in children with Confirmed TB than in children with Unlikely TB (9.5 mg/L vs. 2.9 mg/L, P-value = .03). At a 10 mg/L cut-off, CRP sensitivity was 50.0% (95% confidence interval [CI], 37.0-63.0) among Confirmed TB cases and specificity was 63.3% (95% CI, 54.7-71.3) among children with Unlikely TB. Sensitivity increased to 56.5% (95% CI, 43.3-69.0) at the 5 mg/L cut-off, but specificity decreased to 54.0% (95% CI, 45.3-62.4). The area under the ROC curve was 0.59 (95% CI, 0.51-0.67), and the highest sensitivity achieved was 66.1% at a specificity of 46.8%.

CONCLUSIONS

CRP levels were low in children with pulmonary TB, and CRP was unable to achieve the accuracy targets for a TB triage test.

Acute Phase Proteins Are Baseline Predictors of Tuberculosis Treatment Failure

Systemic inflammation is a characteristic feature of pulmonary tuberculosis (PTB). Whether systemic inflammation is associated with treatment failure in PTB is not known. Participants, who were newly diagnosed, sputum smear and culture positive individuals with drug-sensitive PTB, were treated with standard anti-tuberculosis treatment and classified as having treatment failure or microbiological cure. The plasma levels of acute phase proteins were assessed at baseline (pre-treatment). Baseline levels of C-reactive protein (CRP), alpha-2 macroglobulin (a2M), Haptoglobin and serum amyloid P (SAP) were significantly higher in treatment failure compared to cured individuals. ROC curve analysis demonstrated the utility of these individual markers in discriminating treatment failure from cure. Finally, combined ROC analysis revealed high sensitivity and specificity of 3 marker signatures comprising of CRP, a2M and SAP in distinguishing treatment failure from cured individuals with a sensitivity of 100%, specificity of 100% and area under the curve of 1. Therefore, acute phase proteins are very accurate baseline predictors of PTB treatment failure. If validated in larger cohorts, these markers hold promise for a rapid prognostic testing for adverse treatment outcomes in PTB.

CXCL1: A new diagnostic biomarker for human tuberculosis discovered using Diversity Outbred mice

More humans have died of tuberculosis (TB) than any other infectious disease and millions still die each year. Experts advocate for blood-based, serum protein biomarkers to help diagnose TB, which afflicts millions of people in high-burden countries. However, the protein biomarker pipeline is small. Here, we used the Diversity Outbred (DO) mouse population to address this gap, identifying five protein biomarker candidates. One protein biomarker, serum CXCL1, met the World Health Organization’s Targeted Product Profile for a triage test to diagnose active TB from latent M.tb infection (LTBI), non-TB lung disease, and normal sera in HIV-negative, adults from South Africa and Vietnam. To find the biomarker candidates, we quantified seven immune cytokines and four inflammatory proteins corresponding to highly expressed genes unique to progressor DO mice. Next, we applied statistical and machine learning methods to the data, i.e., 11 proteins in lungs from 453 infected and 29 non-infected mice. After searching all combinations of five algorithms and 239 protein subsets, validating, and testing the findings on independent data, two combinations accurately diagnosed progressor DO mice: Logistic Regression using MMP8; and Gradient Tree Boosting using a panel of 4: CXCL1, CXCL2, TNF, IL-10. Of those five protein biomarker candidates, two (MMP8 and CXCL1) were crucial for classifying DO mice; were above the limit of detection in most human serum samples; and had not been widely assessed for diagnostic performance in humans before. In patient sera, CXCL1 exceeded the triage diagnostic test criteria (>90% sensitivity; >70% specificity), while MMP8 did not. Using Area Under the Curve analyses, CXCL1 averaged 94.5% sensitivity and 88.8% specificity for active pulmonary TB (ATB) vs LTBI; 90.9% sensitivity and 71.4% specificity for ATB vs non-TB; and 100.0% sensitivity and 98.4% specificity for ATB vs normal sera. Our findings overall show that the DO mouse population can discover diagnostic-quality, serum protein biomarkers of human TB.

More humans die of tuberculosis (TB) than any other infectious disease, yet diagnostic tools remain limited. Here, we used the Diversity Outbred mouse population to discover candidate protein biomarkers of human TB. By applying statistical methods and machine learning to multidimensional data, we identified CXCL1 and MMP8 as the two most promising protein biomarker candidates. When evaluated in samples from human patients, CXCL1 achieved the World Health Organization’s targeted profile for a triage diagnostic test, discriminating active TB from important clinical differential diagnoses: latent Mtb infection and non-TB lung disease in HIV-negative adults. Overall, our studies show how a translationally relevant animal population model can accelerate TB biomarker discovery, validation, and testing for humans.

Diagnostic Accuracy of the INSHI Consensus Case Definition for the Diagnosis of Paradoxical Tuberculosis-IRIS

BACKGROUND

The diagnosis of paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) relies on characteristic clinical features synthesized as the International Network for the Study of HIV-associated IRIS (INSHI) case definition. There is no confirmatory laboratory test.

SETTING

Site B HIV-TB clinic in Khayelitsha, Cape Town, South Africa.

METHODS

Using data of participants with HIV-associated tuberculosis starting antiretroviral treatment from a prospective trial evaluating prednisone for TB-IRIS prevention, we applied latent class analysis to model a gold standard for TB-IRIS. The model-predicted probability of TB-IRIS for each participant was used to assess the performance of the INSHI case definition and compare its diagnostic accuracy with several adapted case definitions.

RESULTS

Data for this analysis were complete for 217 participants; 41% developed TB-IRIS. Our latent class model included the following parameters: respiratory symptoms; night sweats; INSHI major criteria 1, 2, and 4; maximum C-reactive protein >90 mg/L; maximum heart rate >120/min; maximum temperature >37.7°C; and preantiretroviral therapy CD4 count <50 cells/µL. The model estimated a TB-IRIS incidence of 43% and had optimal goodness of fit (χ2 = 337, P = 1.0). The INSHI case definition displayed a sensitivity of 0.77 and a specificity of 0.86. Replacing all the minor INSHI criteria with objectives measures (C-reactive protein elevation, fever, and/or tachycardia) resulted in a definition with better diagnostic accuracy, with a sensitivity of 0.89 and a specificity of 0.88.

CONCLUSION

The INSHI case definition identifies TB-IRIS with reasonable accuracy. Amending the case definition by replacing INSHI minor criteria with objective variables improved sensitivity without loss of specificity.

Old biomarkers in tuberculosis management: are they still useful? a systematic review

Introduction: The diagnosis of childhood tuberculosis (TB) can be challenging, given the lack of a gold standard test. Several new biomarkers have been studied for research purposes, but despite encouraging results, they are not used in clinical practice yet. Old biomarkers can be valuable tools in TB management. We conducted a systematic review to provide an update on their possible usefulness in TB patients.Areas covered: C-reactive protein could be useful to rule out TB, due to its high negative predictive value. Moreover, ferritin and erythrocyte sedimentation rates were found to be higher in TB patients with positive sputum smears. The lack of biomarkers decreases during an appropriate treatment course, indicating a poor response to treatment, seems to be correlated with a higher risk of death. Finally, procalcitonin and C-reactive protein seems to be useful in the differential diagnosis with pneumonia.Expert opinion: Old biomarkers are point-of-care tests, cheap and easily interpretable. These characteristics make them particularly useful, especially in TB endemic areas, to better manage patients with TB. Further studies performed in children are essential to implement the use of old biomarkers as diagnostic and prognostic tests.

Prediction and identification of CD4+ T cell epitope for the protective antigens of Mycobacterium tuberculosis

CD4+T cell epitopes plays a key role in anti-tuberculosis (TB) immunity, CD4+T cell epitopes suitable for the domestic population are lacking. Therefore, we predicted and identified novel CD4+T cell epitopes.The bioinformatics software, namely, DNAStar (DNASTAR of the United States), SYFPEITHI (INTERFACTORS INSTITUT Für ZELL Biologie of Germany), RANKPEP, and NetMHC IIpan (National Cancer Institute, United States of America), were used to comprehensively predict the CD4+T cell immune epitope of Mycobacterium TB, and the predicted epitope polypeptide was synthesized by the standard Fmoc scheme. The proliferation of PBMC and CD4+T cells stimulated by peptides was preliminarily detected by the CCK8 method. Then, the candidate polypeptides screened out by the CCK8 method were verified again by the BrdU assay, and flow cytometry was performed to analyze further the extent of their stimulation on the proliferation of CD4+T cells. The changes in the secreted cytokines IFN-γ, TNF-α, IL-2, and IL-10 before and after the candidate polypeptide stimulation of CD4+T lymphocytes were detected by ELISA. The preliminary humoral immunity test was conducted by indirect ELISA to evaluate the serological diagnostic value of the CD4+T cell epitope polypeptide.In this study, 5 novel candidate CD4+T cell epitope polypeptides with the amino acid sequences of LQGQWRGAAGTAAQA, PVTLAETGSTLLYPL, AAAWGGSGSEAYQGV, QFVYAGAMSGLLDPS, and KAALTRTASNMNAAA and others that have not been reported in the research were predicted. For convenience, the 5 candidates were successively named as P39, P50, P40, P185, and P62. P39, P62, and the mixed peptide P39+P62 could effectively induce the proliferation of CD4+T cells and increase the secretion of IFN-γ, TNF-α, and IL-2 from the CD4+T cells, while reducing the content of IL-10. The serological test showed that the sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of P39 were 75%, 67.71%, and 0.844, respectively. The sensitivity, specificity, and AUC of P62 were 91.66%, 46.87%, and 0.649, respectively. The sensitivity of the mixed peptide P39+P62 was 95.83%, the specificity was 97.91%, and the AUC was 0.793.The P39 and P62 polypeptides were predicted and identified as potential CD4+T cell immune epitope polypeptides of M. TB. The polypeptide had better diagnosis effect, which provided potential candidate epitope polypeptides for the development of TB-specific diagnosis reagents and novel TB epitope vaccines.

High-sensitivity C-reactive protein in HIV care: Tuberculosis diagnosis and short-term mortality in a cohort of Kenyan HIV patients in the DREAM programme

OBJECTIVE

Tuberculosis (TB) is the leading cause of death in HIV-positive people. In Kenya, 140 000 new TB cases occurred in 2019, and 13 000 HIV-positive patients died due to TB. The objective of this study was to investigate the role of high-sensitivity C-reactive protein (HS-CRP) in TB diagnosis and the prediction of mortality in HIV-positive patients.

METHODS

The IDEA-TB Study enrolled HIV-positive adult patients attending three DREAM centres in Kenya who were suspected of having TB. A lateral flow urine lipoarabinomannan assay (LF-LAM), serum HS-CRP, and GeneXpert MTB/RIF assay (Xpert MTB/RIF) were performed. Six-month survival was evaluated.

RESULTS

A total of 574 patients were enrolled. The median (interquartile range) age, body mass index, and CD4 count were 45 years (37-54 years), 20.5 kg/m² (18.5-23.69 kg/m²), and 477 cells/mL (290-700 cells/mL), respectively. TB was confirmed in 87 (15.2%) patients. Concordance between the Xpert MTB/RIF and LF-LAM tests was 87.1%. HS-CRP was higher in TB patients (35.39 mg/l vs 9.21 mg/l). Malnutrition and elevated HS-CRP were associated with TB: odds ratio (OR) 2.5 (95% confidence interval (CI) 1.14-5.72) and OR 6.6 (95% CI 3.87-11.52), respectively. Nine (1.6%) patients died during follow-up. No single factor was associated with mortality. Only the combination of malnutrition and elevated HS-CRP was highly predictive of death (odds ratio (OR) 9.8, 95% CI 1.88-50.95); the association was stronger in TB patients (33.3% vs 1.0%; OR 47.6, 95% CI 7.03-322.23).

CONCLUSION

TB diagnosis in HIV-positive patients remains challenging. HS-CRP could play a role in predicting early mortality in symptomatic patients.

C-Reactive Protein Testing for Active Tuberculosis among Inpatients without HIV in Uganda: a Diagnostic Accuracy Study

The objective of this prospective cross-sectional study, conducted at a national referral hospital in Kampala, Uganda, was to determine diagnostic performance of serum C-reactive protein (CRP) as a triage test for tuberculosis (TB) among HIV-seronegative inpatients. We calculated the sensitivity, specificity, positive and negative likelihood ratios, and positive and negative predictive values to determine the diagnostic performance of a CRP enzyme-linked immunosorbent assay (ELISA) (Eurolyser) in comparison to that of a reference standard of Mycobacterium tuberculosis culture on two sputum samples. We constructed receiver operating curves and reported performance in reference to the manufacturer's cutoff and also to a threshold chosen to achieve sensitivity of >90%, in accordance with the WHO's target-product profile for a triage test. Among 119 HIV-seronegative inpatients, 46 (39%) had culture-positive pulmonary TB. In reference to M. tuberculosis culture, CRP had a sensitivity of 78% (95% confidence interval [CI], 64 to 89%) and a specificity of 52% (95% CI, 40 to 64%) at the manufacturer's threshold of 10 mg/liter. At a threshold of 1.5 mg/liter, the sensitivity was 91% (95% CI, 79 to 98%) but the specificity was only 21% (95% CI, 12 to 32%). Performance did not differ when stratified by illness severity at either threshold. In conclusion, among HIV-seronegative inpatients, CRP testing performed substantially below targets for a TB triage test. Additional studies among HIV-seronegative individuals in clinics and community settings are needed to assess the utility of CRP for TB screening.

Altered systemic levels of acute phase proteins in tuberculous lymphadenitis and modulation after treatment

Background

Pulmonary tuberculosis (PTB) is characterized by elevated levels of acute phase proteins (APPs), but their association with tuberculous lymphadenitis (TBL) is poorly studied.

Methods

We examined the systemic levels of APPs (alpha-2-macroglobulin [⍺-2MG], serum amyloid A [SAA], C-reactive protein [CRP] and haptoglobin [Hp]) in TBL, PTB, latent tuberculosis (LTB) and healthy controls (HC) at baseline and in TBL after the completion of anti-tuberculosis treatment (ATT). We have also examined the association of these proteins with lymph node (LN) size, culture grade and multiple versus single LN involvement.

Results

TBL individuals exhibited increased systemic levels of ⍺-2MG, SAA, CRP and Hp in comparison to HCs and increased CRP levels in comparison to LTB individuals. TBL individuals also exhibited decreased systemic levels of Hp compared to PTB individuals. APPs were not significantly associated with LN size, LN involvement and culture grade, indicating a lack of association with disease severity. Following ATT, post-treatment levels of ⍺-2MG, CRP and Hp were significantly diminished compared to pre-treatment levels.

Conclusion

TBL disease is characterized by altered levels of APPs at baseline and modulated following treatment, indicating the presence of systemic inflammation.

Interleukin 8 and Pentaxin (C-Reactive Protein) as Potential New Biomarkers of Bovine Tuberculosis

Bovine tuberculosis (bTB) is caused by Mycobacterium bovis. During the early stage of infection, greater than 15% of M. bovis-infected cattle shed mycobacteria through nasal secretions, which can be detected by nested PCR.

Bovine tuberculosis (bTB) is caused by Mycobacterium bovis. During the early stage of infection, greater than 15% of M. bovis-infected cattle shed mycobacteria through nasal secretions, which can be detected by nested PCR. To compare the differences in the protein profiles of M. bovis-infected cattle that were nested PCR positive (bTB_PCR-P) and M. bovis-infected cattle that were nested PCR negative (bTB_PCR-N) and to screen for biomarkers that will facilitate the early and accurate detection of bTB, we investigated the protein expression profiles of serum and bovine purified protein derivative (PPD-B)-stimulated plasma among bTB_PCR-P (n = 20), bTB_PCR-N (n = 20), and uninfected cattle (NC; n = 20) by iTRAQ labeling coupled with two-dimensional liquid chromatography-tandem mass spectrometry (iTRAQ-2D LC-MS/MS). After comprehensive analysis, we selected 15 putative differentially expressed serum proteins and 15 plasma proteins for validation by parallel reaction monitoring (PRM) with the same cohort used in the iTRAQ analysis. Four serum and five PPD-B-stimulated proteins were confirmed in follow-up enzyme-linked immunosorbent assays. PPD-B-stimulated interleukin 8 (IL-8) displayed the potential to differentiate M. bovis-infected cattle from NC, with an area under the curve (AUC) value of 0.9662, while PPD-B-stimulated C-reactive protein (CRP) displayed the potential to differentiate bTB_PCR-P from bTB_PCR-N, with an AUC value of 1.00. Finally, double-blind testing with 244 cattle indicated that the PPD-B-stimulated IL-8 test exhibited good agreement with traditional tests (κ > 0.877) with a >90% relative sensitivity and a >98% relative specificity; the PPD-B-stimulated CRP test displayed good agreement with nested PCR (κ = 0.9117), with an observed 94% relative sensitivity and 97% relative specificity. Therefore, the PPD-B-stimulated IL-8 and CRP tests could be used to detect bTB and to differentiate bTB_PCR-P from bTB_PCR-N.

Plasma levels of C-reactive protein, matrix metalloproteinase-7 and lipopolysaccharide-binding protein distinguish active pulmonary or extrapulmonary tuberculosis from uninfected controls in children

The immune profile associated with distinct clinical forms of tuberculosis (TB) has been extensively described for adult populations. Nevertheless, studies describing immune determinants of pulmonary or extrapulmonary TB (PTB or EPTB, respectively) in children are scarce. Here, we retrospectively assessed plasma levels of several mediators of inflammation in age and sex-matched children from South India presenting with PTB (n = 14) or EPTB (n = 22) as well as uninfected healthy controls (n = 19) to identify biomarkers that could accurately distinguish different TB clinical forms. Furthermore, we performed exploratory analyses testing the influence of sex on the systemic inflammatory profile. The analyses identified a biosignature of 10 biomarkers capable of distinguishing the three clinical groups simultaneously. Machine-learning decision trees indicated that C-reactive protein (CRP), matrix metalloproteinase (MMP)-7 and lipopolysaccharide-binding protein (LBP) were the markers that, when combined, displayed the highest accuracy in identifying the clinical groups. Additional exploratory analyses suggested that the disease signatures were highly influenced by sex. Therefore, sex differentially impacted status of systemic inflammation, immune activation and tissue remodeling in children with distinct clinical forms of TB. Regardless of such nuances related to biological sex, MMP-7, CRP and LBP were strong discriminators of active TB and thus could be considered as biomarkers useful in discrimination different TB clinical forms. These observations have implications on our understanding of the immunopathology of both clinical forms of TB in pediatric patients. If validated by other studies in the future, the combination of identified biomarkers may help development of point-of-care diagnostic or prognostic tools.

Combining urine lipoarabinomannan with antibody detection as a simple non-sputum-based screening method for HIV-associated tuberculosis

Background

Simple methods for the accurate triaging and screening of HIV-associated tuberculosis (TB) are urgently needed. We hypothesized that combining serum antibody with urine lipoarabinomannan (U-LAM) detection can improve the detection of HIV-associated TB.

Methods

We performed a case-control study with sampling from a prospective study of South African HIV-infected subjects who were screened for TB prior to initiating antiretroviral therapy. Sera from all available TB cases (n = 74) and randomly selected non-TB controls (n = 30), all tested for U-LAM, sputum microscopy, GeneXpert, and cultures, were evaluated for antibodies to LAM and arabinomannan (AM). Diagnostic logistic regression models for TB were developed based on the primary test results and the additive effect of antibodies with leave-one-out cross-validation.

Results

Antibody responses to LAM and AM correlated strongly (p<0.0001), and IgG and IgM reactivities were significantly higher in TB than non-TB patients (p<0.0001). At 80% specificity, the target specificity for a non-sputum-based simple triage/screening test determined by major TB stakeholders, combining U-LAM with IgG detection significantly increased the sensitivity for HIV-associated TB to 92% compared to 30% for U-LAM alone (p<0.001). Sputum microscopy combined with IgG detection increased sensitivity to 88% compared to 31% for microscopy alone, and Xpert with IgG increased sensitivity to 96% and 99% compared to 57% for testing one, and 70% for testing two sputa with Xpert alone, respectively.

Conclusion

Combining U-LAM with serum antibody detection could provide a simple low-cost method that meets the requirements for a non-sputum-based test for the screening of HIV-associated TB.

Point-of-care C-reactive protein and risk of early mortality among adults initiating antiretroviral therapy

OBJECTIVES

In resource-limited settings, mortality in the initial months following antiretroviral therapy (ART) initiation remains unacceptably high. Novel tools to identify patients at highest risk of poor outcomes are needed. We evaluated whether elevated C-reactive protein (CRP) concentrations predict poor outcomes among people living with HIV (PLWH) initiating ART.

METHODS

We enrolled and followed for 3-months consecutive PLWH with pre-ART CD4 T-cell counts 350 cells/μl or less initiating ART from two HIV clinics in Uganda. Pre-ART CRP concentrations were measured from capillary blood using a point-of-care (POC) assay. After excluding patients with prevalent tuberculosis - the leading cause of HIV death - we measured 3-month mortality rates using Kaplan-Meier curves, used Cox regression to compare differences in survival, and used logistic regression to compare differences in the odds of opportunistic infections, between patients with and without elevated POC CRP (≥8 mg/l).

RESULTS

Of 1293 patients included [median CD4 T-cell count 181 (interquartile range 82-278)], 23 (1.8%) died within 3 months, including 19 of 355 (5.4%) with elevated POC CRP and four of 938 (0.4%) with nonelevated POC CRP. Eighty-six (6.7%) patients were diagnosed with opportunistic infections, including 39 of 355 (11.0%) with elevated POC CRP and 47 of 938 (5.0%) with nonelevated POC CRP. Elevated POC CRP was associated with mortality (adjusted hazard ratio 10.87, 95% confidence interval 3.64-32.47) and opportunistic infection (adjusted odds ratio 1.95, 95% confidence interval 1.23-3.07).

CONCLUSION

Among PLWH with advanced HIV, elevated pre-ART POC CRP concentrations are associated with early mortality and opportunistic infections. Pre-ART POC CRP testing may reduce mortality by identifying patients at high risk for poor outcomes.

An Observational Case-Control Study to Determine Human Immunodeficiency Virus and Host Factor Influence on Biomarker Distribution and Serodiagnostic Potential in Adult Pulmonary Tuberculosis

Influence of host factors, including human immunodeficiency virus (HIV) co-infection, on the distribution and diagnostic potential of previously evaluated biomarkers of pulmonary tuberculosis (PTB), such as anti-antigen 60 (A60) immunoglobulin (Ig) G, anti-A60 IgA, and C-reactive protein (CRP), remain unclear. Anti-A60 IgG, anti-A60 IgA, and CRP in PTB and non-PTB patient sera (n = 404, including smear-positive/negative, culture-positive (SPCP/SNCP) and HIV+ve/-ve) were measured by enzyme-linked immunoassay and statistically analysed. In multinomial logistic regression, expectoration, chest pain, wasting, and culture count positively associated with CRP (p < 0.001), while smear count positively associated with anti-A60 IgG (p = 0.090). Expectoration and enlarged lymph nodes negatively associated with anti-A60 IgA (p = 0.018). Biomarker distribution and diagnostic potential varied significantly by symptoms and bacilli burden, and across different PTB subpopulations. CRP was correlated poorly with anti-A60 antibodies, while anti-A60 IgA and IgG were correlated in non-tuberculosis (TB) and SPCP patients (p < 0.001). When combined, anti-A60 IgG and CRP best discriminated SPCP/HIV-ve from non-TB (AUC: 0.838, 95% CI: 0.783⁻0.894), while anti-A60 IgA and CRP performed best in discriminating HIV+ve PTB from non-TB (AUC: 0.687, 95% CI: 0.598⁻0.777). Combined CRP and anti-A60 antibodies had significantly reduced accuracy in SNCP and SNCP/HIV+ve compared to SPCP/HIV-ve subpopulations. The complex relationships between host factors and biomarkers suggest their limited utility, especially in SNCP/HIV+ve subpopulations, highlighting the importance of examining host response and immune biomarkers across relevant patient subpopulations.

Plasma Profiles of Inflammatory Markers Associated With Active Tuberculosis in Antiretroviral Therapy-Naive Human Immunodeficiency Virus-Positive Individuals

Background

Diagnosis of tuberculosis (TB) in human immunodeficiency virus (HIV)-coinfected individuals is challenging. We hypothesized that combinations of inflammatory markers could facilitate identification of active TB in HIV-positive individuals.

Methods

Participants were HIV-positive, treatment-naive adults systematically investigated for TB at Ethiopian health centers. Plasma samples from 130 subjects with TB (HIV⁺/TB⁺) and 130 subjects without TB (HIV⁺/TB⁻) were tested for concentration of the following markers: CCL5, C-reactive protein (CRP), interleukin (IL)-6, IL12-p70, IL-18, IL-27, interferon-γ-induced protein-10 (IP-10), procalcitonin (PCT), and soluble urokinase-type plasminogen activator receptor (suPAR). Analyzed markers were then assessed, either individually or in combination, with regard to infection status, CD4 cell count, and HIV ribonucleic acid (RNA) levels.

Results

The HIV⁺/TB⁺ subjects had higher levels of all markers, except IL12p70, compared with HIV⁺/TB⁻ subjects. The CRP showed the best performance for TB identification (median 27.9 vs 1.8 mg/L for HIV⁺/TB⁺ and HIV⁺/TB⁻, respectively; area under the curve [AUC]: 0.80). Performance was increased when CRP was combined with suPAR analysis (AUC, 0.83 [0.93 for subjects with CD4 cell count <200 cells/mm³]). Irrespective of TB status, IP-10 concentrations correlated with HIV RNA levels, and both IP-10 and IL-18 were inversely correlated to CD4 cell counts.

Conclusions

Although CRP showed the best single marker discriminatory potential, combining CRP and suPAR analyses increased performance for TB identification.

High Sensitivity C Reactive Protein: An Adjunct Diagnosis in Ruling Out Pediatric Tuberculosis

The utility of C-reactive protein (CRP) as a marker of disease severity, therapeutic response and prognosis in tuberculosis has been suggested. This study aims to determine the levels of high sensitivity CRP (hs CRP) among the pediatric tuberculosis cases. A case control study was conducted on 60 clinically diagnosed (clinical findings and radiography and/or contact history and/or Mantoux test) or microbiologically confirmed (smear and/or culture and/or Cartridge based Nucleic Acid Amplification test positive) pediatric tuberculosis cases ≤ 12 years. hs CRP levels were estimated in the cases and healthy controls using ELISA. Median levels of serum hs CRP were significantly higher in pediatric tuberculosis cases (25 mg/l) as compared to controls (0.530 mg/l). No significant correlation was found with age, gender, site of tuberculosis or presence of dissemination. Lower levels were found with palpable lymphadenopathy. Levels were not significantly different between microbiologically confirmed cases and those who were negative by one or more of the microbiological tests of staining, culture and cartridge based nucleic acid amplification test. hs CRP can be used in diagnostic algorithms of pediatric tuberculosis to rule out tuberculosis. Further studies could help in determining the prognostic and therapeutic response of hs CRP among children leading to better management.

Diagnostic performance of blood inflammatory markers for tuberculosis screening in people living with HIV

BACKGROUND

Approaches to screening for active tuberculosis (TB) among people living with HIV are inadequate, leading to missed diagnoses and poor implementation of preventive therapy.

METHODS

Consecutive HIV-infected adults hospitalized at Mulago Hospital (Kampala, Uganda) between June 2011 and July 2013 with a cough ≥ 2 weeks were enrolled. Patients underwent extensive evaluation for pulmonary TB. Concentrations of 43 cytokines/chemokines were measured at the same time point as C-reactive protein (CRP) in banked plasma samples using commercially-available multiplex kits. Advanced classification algorithms were used to rank cytokines/chemokines for their ability to identify TB, and to model the specificity of the top-ranked cytokines/chemokines individually and in combination with sensitivity constrained to ≥ 90% as recommended for TB screening.

RESULTS

The median plasma level of 5 biomarkers (IL-6, INF-γ, MIG, CRP, IL-18) was significantly different between patients with and without TB. With sensitivity constrained to 90%, all had low specificity with IL-6 showing the highest specificity (44%; 95% CI 37.4-49.5). Biomarker panels were found to be more valuable than any biomarker alone. A panel combining IFN-γ and IL-6 had the highest specificity (50%; 95% CI 46.7-53.3). Sensitivity remained high (>85%) for all panels among sputum smear-negative TB patients.

CONCLUSIONS

Direct measurement of unstimulated plasma cytokines/chemokines in peripheral blood is a promising approach to TB screening. Cytokine/chemokine panels retained high sensitivity for smear-negative TB and achieved improved specificity compared to individual cytokines/chemokines. These markers should be further evaluated in outpatient settings where most TB screening occurs and where other illnesses associated with systematic inflammation are less common.

Evaluation of Tuberculosis Treatment Response With Serial C-Reactive Protein Measurements

Background

Novel biomarkers are needed to assess response to antituberculosis therapy in smear-negative patients.

Methods

To evaluate the utility of C-reactive protein (CRP) in monitoring response to antituberculosis therapy, we conducted a post hoc analysis on a cohort of adults with symptoms of tuberculosis and negative sputum smears in a high–tuberculosis and HIV prevalence setting in KwaZulu-Natal, South Africa. Serial changes in CRP, weight, and hemoglobin were evaluated over 8 weeks.

Results

Four hundred twenty-one participants being evaluated for smear-negative tuberculosis were enrolled, and 33 were excluded. Two hundred ninety-five were treated for tuberculosis (137 confirmed, 158 possible), and 93 did not have tuberculosis. One hundred and eighty-three of 213 (86%) participants who agreed to HIV testing were HIV positive. At week 8, the on-treatment median CRP reduction in the tuberculosis group (interquartile range [IQR]) was 79.5% (25.4% to 91.7%), the median weight gain was 2.3% (−1.0% to 5.6%), and the median hemoglobin increase was 7.0% (0.8% to 18.9%); P < .0001 for baseline to week 8 comparison of absolute median values. Only CRP changed significantly at week 2 (median reduction [IQR], 75.1% [46.9% to 89.2%]) in the group with confirmed tuberculosis and in the possible tuberculosis group (median reduction [IQR], 49.0% [−0.4% to 80.9%]). Failure of CRP to reduce to ≤55% of the baseline value at week 2 predicted hospitalization or death in both tuberculosis groups, with 99% negative predictive value.

Conclusions

Change in CRP may have utility in early evaluation of response to antituberculosis treatment and to identify those at increased risk of adverse outcomes.

Acute phase proteins and IP-10 as triage tests for the diagnosis of tuberculosis: systematic review and meta-analysis

OBJECTIVES

We examined the data reported in studies for diagnostic purposes and to discuss whether their intended use could be extended to triage, as rule-in or rule-out tests to select individuals who should undergo further confirmatory tests.

METHODS

We searched Scopus, PubMed and Web of Science with the terms 'acute phase proteins,' 'IP-10,' 'tuberculosis,' 'screening' and 'diagnosis,' extracted the sensitivity and specificity of the biomarkers and explored methodologic differences to explain performance variations. Summary estimates were calculated using random-effects models for overall pooled accuracy. The hierarchical summary receiver operating characteristic model was used for meta-analysis.

RESULTS

We identified 14, four and one studies for C-reactive protein (CRP), interferon γ-induced protein 10 (IP-10) and alpha-1-acid glycoprotein (AGP). The pooled CRP sensitivity/specificity (95% confidence interval) was 89% (80-96) and 57% (36-65). Sensitivity/specificity were higher in high-tuberculosis-burden countries (90%/64%), HIV-infected individuals (91%/61%) and community-based studies (90%/62%). IP-10 sensitivity/specificity in TB vs. non-TB studies was 85%/63% and in TB and HIV coinfected vs. other lung conditions 94%/21%. However, IP-10 studies included diverse populations and a high risk of bias, resulting in very low-quality evidence. AGP had 86%/93% sensitivity/specificity.

CONCLUSIONS

Few studies have evaluated CRP, IP-10 and AGP for the triage of symptomatic patients. Their high sensitivity and moderate specificity warrant further prospective studies exploring whether their combined use could optimize performance.

Soluble CD14 as a Diagnostic Biomarker for Smear-Negative HIV-Associated Tuberculosis

Sputum smear-negative HIV-associated active tuberculosis (TB) is challenging to diagnose. CD14 is a pattern recognition receptor that is known to mediate monocyte activation. Prior studies have shown increased levels of soluble CD14 (sCD14) as a potential biomarker for TB, but little is known about its value in detecting smear-negative HIV-associated TB. We optimized a sandwich ELISA for the detection of sCD14, and tested sera from 56 smear-negative South African (39 culture-positive and 17 culture-negative) HIV-infected pulmonary TB patients and 24 South African and 43 US (21 positive and 22 negative for tuberculin skin test, respectively) HIV-infected controls. SCD14 concentrations were significantly elevated in smear-negative HIV-associated TB compared with the HIV-infected controls (p < 0.0001), who had similar concentrations, irrespective of the country of origin or the presence or absence of latent M. tuberculosis infection (p = 0.19). The culture-confirmed TB group had a median sCD14 level of 2199 ng/mL (interquartile range 1927-2719 ng/mL), versus 1148 ng/mL (interquartile range 1053-1412 ng/mL) for the South African controls. At a specificity of 96%, sCD14 had a sensitivity of 95% for culture-confirmed smear-negative TB. These data indicate that sCD14 could be a highly accurate biomarker for the detection of HIV-associated TB.

Predictive value of C-reactive protein for tuberculosis, bloodstream infection or death among HIV-infected individuals with chronic, non-specific symptoms and negative sputum smear microscopy

BACKGROUND

C-reactive protein (CRP) is an inflammatory biomarker that may identify patients at risk of infections or death. Mortality among HIV-infected persons commencing antiretroviral therapy (ART) is often attributed to tuberculosis (TB) or bloodstream infections (BSI).

METHODS

In two district hospitals in southern Malawi, we recruited HIV-infected adults with one or more unexplained symptoms present for at least one month (weight loss, fever or diarrhoea) and negative expectorated sputum microscopy for TB. CRP determination for 452 of 469 (96%) participants at study enrolment was analysed for associations with TB, BSI or death to 120 days post-enrolment.

RESULTS

Baseline CRP was significantly elevated among patients with confirmed or probable TB (52), BSI (50) or death (60) compared to those with no identified infection who survived at least 120 days (269). A CRP value of >10 mg/L was associated with confirmed or probable TB (adjusted odds ratio 5.7; 95% CI 2.6, 14.3; 87% sensitivity) or death by 30 days (adjusted odds ratio 9.2; 95% CI 2.2, 55.1; 88% sensitivity). CRP was independently associated with TB, BSI or death, but the prediction of these endpoints was enhanced by including haemoglobin (all outcomes), CD4 count (BSI, death) and whether ART was started (death) in logistic regression models.

CONCLUSION

High CRP at the time of ART initiation is associated with TB, BSI and early mortality and so has potential utility for stratifying patients for intensified clinical and laboratory investigation and follow-up. They may also be considered for empirical treatment of opportunistic infections including TB.

Diagnostic accuracy of C-reactive protein for active pulmonary tuberculosis: a meta-analysis

SETTING

Systematic screening for active pulmonary tuberculosis (PTB) is recommended for high-risk populations, including people living with the human immunodeficiency virus (PLHIV); however, currently recommended TB screening tools are inadequate for most high-burden settings.

OBJECTIVE

To determine whether C-reactive protein (CRP) possesses the necessary test characteristics to screen individuals for active PTB.

DESIGN

We performed a systematic review and meta-analysis of studies evaluating the diagnostic accuracy of CRP (10 mg/l cut-off point) for culture-positive PTB. Pooled diagnostic accuracy estimates were generated using random-effects meta-analysis for out-patients and in-patients, and for pre-specified subgroups based on HIV status and test indication.

RESULTS

We identified nine unique studies enrolling 1793 adults from out-patient (five studies, 1121 patients) and in-patient settings (five studies, 672 patients), 72% of whom had confirmed HIV infection. Among out-patients, CRP had high sensitivity (93%, 95%CI 88-98) and moderate specificity (60%, 95%CI 40-75) for active PTB. Specificity was lowest among in-patients (21%, 95%CI 6-52) and highest among out-patients undergoing TB screening (range 58-81%). There was no difference in summary estimates by HIV status.

CONCLUSION

CRP, which is available as a simple, inexpensive and point-of-care test, can be used to screen PLHIV presenting for routine HIV/AIDS (acquired immune-deficiency syndrome) care for active TB.

Point-of-care C-reactive protein-based tuberculosis screening for people living with HIV: a diagnostic accuracy study

Background

Symptom-based screening for tuberculosis (TB) is recommended for all people living with HIV (PLHIV) resulting in unnecessary Xpert MTB/RIF testing for the vast majority of individuals living in TB endemic areas and thus, poor implementation of intensified case finding (ICF) and TB preventive therapy. Novel approaches to TB screening are therefore critical in achieving global targets for TB elimination.

Methods

In a prospective study of PLHIV with CD4+ T-cell count ≤350 cells/uL initiating antiretroviral therapy (ART) from two HIV/AIDS clinics in Uganda, we evaluated the performance of C-reactive protein (CRP) measured using a rapid and inexpensive point-of-care (POC) assay as a screening tool for active pulmonary TB.

Findings

Of 1177 HIV-infected adults (median CD4+ T-cell count 168 cells/µL) enrolled, 163 (14%) had culture-confirmed TB. POC CRP had 89% (145/163) sensitivity and 72% (731/1014) specificity for culture-confirmed TB. Compared to the WHO symptom screen, POC CRP had lower sensitivity (difference −7% [95% CI: −12 to −2], p=0.002) but substantially higher specificity (difference +58% [95% CI: +61 to +55], p<0.0001). When Xpert MTB/RIF results were used as the reference standard, sensitivity of POC CRP and the WHO symptom screen were similar (94% [79/84] vs. 99% [83/84]; difference −5% [95% CI: −12 to +2], p=0.10).

Interpretation

The performance characteristics of CRP support its use as a TB screening test for PLHIV with CD4+ T-cell count ≤350 cells/µL initiating ART. HIV/AIDS programs should consider POC CRP-based TB screening to improve the efficiency of ICF and increase uptake of TB preventive therapy.

FUNDING

National Institutes of Health; Presidential Emergency Plan for AIDS Relief; University of California, San Francisco, Nina Ireland Program for Lung Health

Diagnostic Outcomes After Chest Radiograph Interpretation in Patients With Suspected Tuberculosis and Negative Sputum Smears in a High-Burden Human Immunodeficiency Virus and Tuberculosis Setting

BACKGROUND

Evaluation of patients with suspected tuberculosis and negative sputum smears for acid-fast bacilli (AFB) is challenging, especially in high human immunodeficiency virus coinfection settings where sputum smears have lower sensitivity for detecting AFB.

METHODS

We examined the utility of chest radiographs for detecting smear-negative pulmonary tuberculosis. Three hundred sixty sputum smear-negative patients who were referred from primary care clinics in the KwaZulu-Natal province of South Africa were evaluated. Chest radiographs were read by experienced pulmonologists using a previously validated Chest X-Ray Reading and Recording System (CRRS).

RESULTS

Agreement between observers using CRRS was high at 91% with a Cohen's kappa of 0.64 (95% confidence interval [CI] = 0.52-0.76). Against a reference standard of sputum culture, sensitivity was 93% (95% CI = 86%-97%), whereas specificity was 14% (95% CI = 10%-19%). Performance against clinical diagnosis (following World Health Organization guidelines) was similar with sensitivity of 92% (95% CI = 88%-95%) and specificity of 20% (95% CI = 13%-28%).

CONCLUSION

The low specificity of CRRS in this setting indicates poor diagnostic utility for detecting pulmonary tuberculosis.

A combination of baseline plasma immune markers can predict therapeutic response in multidrug resistant tuberculosis

OBJECTIVE

To identify plasma markers predictive of therapeutic response in patients with multidrug resistant tuberculosis (MDR-TB).

METHODS

Fifty HIV-negative patients with active pulmonary MDR-TB were analysed for six soluble analytes in plasma at the time of initiating treatment (baseline) and over six months thereafter. Patients were identified as sputum culture positive or negative at baseline. Culture positive patients were further stratified by the median time to sputum culture conversion (SCC) as fast responders (< 76 days) or slow responders (≥ 76 days). Chest X-ray scores, body mass index, and sputum smear microscopy results were obtained at baseline.

RESULTS

Unsupervised hierarchical clustering revealed that baseline plasma levels of IP-10/CXCL10, VEGF-A, SAA and CRP could distinguish sputum culture and cavitation status of patients. Among patients who were culture positive at baseline, there were significant positive correlations between plasma levels of CRP, SAA, VEGF-A, sIL-2Rα/CD40, and IP-10 and delayed SCC. Using linear discriminant analysis (LDA) and Receiver Operating Curves (ROC), we showed that a combination of MCP-1/CCL2, IP-10, sIL-2Rα, SAA, CRP and AFB smear could distinguish fast from slow responders and were predictive of delayed SCC with high sensitivity and specificity.

CONCLUSION

Plasma levels of specific chemokines and inflammatory markers measured before MDR-TB treatment are candidate predictive markers of delayed SCC. These findings require validation in a larger study.

The performance of the TBAg/PHA ratio in the diagnosis of active TB disease in immunocompromised patients

OBJECTIVES

The results of the T-SPOT.TB (T-SPOT) assay are reduced in immunocompromised patients with active tuberculosis (ATB), and it is difficult using T-SPOT results to distinguish ATB from latent tuberculosis infection (LTBI) in this condition. The aim of this study was to determine the performance of the TBAg/PHA ratio in T-SPOT assay in the diagnosis of ATB in immunocompromised patients.

METHODS

One hundred and forty three immunocompromised ATB patients and 124 LTBI individuals were diagnosed according to conventional tests and T-SPOT assay.

RESULTS

The results of T-SPOT assay are of no value in the diagnosis of ATB in immunocompromised patients. However, the number of phytohaemagglutinin (PHA) spot-forming cells (sfc) in T-SPOT assay was substantially decreased in immunocompromised ATB patients compared with that in LTBI individuals. Receiver operating characteristic (ROC) analysis revealed that a further calculation of the TBAg/PHA ratio (the larger of the ESAT-6/PHA and CFP-10/PHA) showed a better performance in distinguishing these two diseases. Using the threshold value of 0.316, the sensitivity and specificity for distinguishing immunocompromised ATB patients from LTBI individuals were respectively 79.21 and 94.05%.

CONCLUSIONS

Our findings suggest that the TBAg/PHA ratio might have some significance for the diagnosis of TB disease in immunocompromised patients.

Cost-effectiveness of triage testing for facility-based systematic screening of tuberculosis among Ugandan adults

BACKGROUND

Systematic screening is often proposed as a way to improve case finding for tuberculosis (TB), but the cost-effectiveness of specific strategies for systematic screening remains poorly studied.

METHODS

We constructed a Markov-based decision analytic model to analyse the cost-effectiveness of triage testing for TB in Uganda, compared against passive case detection with Xpert MTB/RIF. We assumed a triage algorithm whereby all adults presenting to healthcare centres would be screened for cough, and those with cough of at least 2 weeks would receive the triage test, with positive triage results confirmed by Xpert MTB/RIF. We adopted the perspective of the TB control sector, using a primary outcome of the cost per year of life gained (YLG) over a lifetime time horizon.

RESULTS

Systematic screening in a population with a 5% underlying prevalence of TB was estimated to cost US$610 per YLG (95% uncertainty range US$200-US$1859) with chest X-ray (CXR) (US$5 per test, specificity 0.67), or US$588 (US$221-US$1746) with C reactive protein (CRP) (US$3 per test, specificity 0.59). In addition to the cost and specificity of the triage test, cost-effectiveness was most sensitive to the underlying prevalence of TB, monthly risk of mortality in people with untreated TB and the proportion of patients with TB who would be treated in the absence of systematic screening.

CONCLUSIONS

To optimise the cost-effectiveness of facility-based systematic screening of TB with a triage test, it must be carried out in a high-risk population, or use triage tests that are cheaper or more specific than CXR or CRP.

Inverting the pyramid: increasing awareness of mycobacterial sepsis in sub-Saharan Africa

Disseminated Mycobacterium tuberculosis is a leading cause of bloodstream infection and severe sepsis in sub-Saharan African settings with a high burden of tuberculosis (TB) and human immunodeficiency virus (HIV) infection. Despite the high prevalence of M. tuberculosis bacteremia in these settings it is under-recognized. This is in part because timely diagnosis of M. tuberculosis bacteremia is difficult using traditional TB diagnostics. Novel triage algorithms and rapid diagnostic tests are needed to expedite the identification and treatment of patients with severe sepsis due to M. tuberculosis bacteremia. In this article, we emphasize the importance of M. tuberculosis bacteremia as an under-recognized etiology of severe sepsis, and discuss the potential role of two emerging rapid diagnostic tests in the triage and prognostication of critically ill patients with advanced HIV infection and suspected disseminated M. tuberculosis. We conclude with the recommendation that clinicians in high TB-HIV burden settings strongly consider empiric anti-tuberculosis treatment in patients with advanced HIV infection and severe sepsis in the appropriate clinical context. Future studies are needed to assess diagnostic and prognostic algorithms for severe sepsis caused by disseminated M. tuberculosis in these settings, and the safety, efficacy, and duration of empiric anti-tuberculosis treatment.

Differential Levels of Alpha-2-Macroglobulin, Haptoglobin and Sero-Transferrin as Adjunct Markers for TB Diagnosis and Disease Progression in the Malnourished Tribal Population of Melghat, India

Lack of diagnostic capacity has been a crucial barrier preventing an effective response to the challenges of malnutrition and tuberculosis (TB). Point-of-care diagnostic tests for TB in immuno-incompetent, malnourished population are thus needed to ensure rapid and accurate detection. The aim of the study was to identify potential biomarkers specific for TB infection and progression to overt disease in the malnourished population of Melghat. A prospective cohort study was conducted in the year 2009 through 2011 in six villages of the Melghat region. 275 participants consisting of malnourished cases with a) active TB (n = 32), b) latent TB infection (n = 90), c) with no clinical or bacteriological signs of active or latent TB (n = 130) and healthy control subjects (n = 23) were recruited for the study. The proteome changes of the host serum in response to Mycobacterium tuberculosis (M.tb) infection were investigated using one dimensional electrophoresis in combination with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Three most differentially expressed proteins; alpha-2-macroglobulin (A-2-M), sero-transferrin and haptoglobin were identified by MALDI-TOF MS analysis, which were up-regulated in the malnourished patients with active TB and down-regulated in the malnourished patients compared with the healthy controls. Additionally, follow-up studies indicated that the expression of these proteins increased to nearly two folds in patients who developed active disease from latent state. Our preliminary results suggest that A-2-M, sero-transferrin and haptoglobin may be clinically relevant host biomarkers for TB diagnosis and disease progression in the malnourished population. This study provides preliminary framework for an in-depth analysis of the biomarkers in larger well-characterized cohorts. Evaluation of these biomarkers in follow-up cases may further aid in improving TB diagnosis.

Association between serum selenium level and conversion of bacteriological tests during antituberculosis treatment

Objective:

To determine whether serum selenium levels are associated with the conversion of bacteriological tests in patients diagnosed with active pulmonary tuberculosis after eight weeks of standard treatment.

Methods:

We evaluated 35 healthy male controls and 35 male patients with pulmonary tuberculosis, the latter being evaluated at baseline, as well as at 30 and 60 days of antituberculosis treatment. For all participants, we measured anthropometric indices, as well as determining serum levels of albumin, C-reactive protein (CRP) and selenium. Because there are no reference values for the Brazilian population, we used the median of the serum selenium level of the controls as the cut-off point. At 30 and 60 days of antituberculosis treatment, we repeated the biochemical tests, as well as collecting sputum for smear microscopy and culture from the patients.

Results:

The mean age of the patients was 38.4 ± 11.4 years. Of the 35 patients, 25 (71%) described themselves as alcoholic; 20 (57.0%) were smokers; and 21 (60.0%) and 32 (91.4%) presented with muscle mass depletion as determined by measuring the triceps skinfold thickness and arm muscle area, respectively. Of 24 patients, 12 (39.2%) were classified as moderately or severely emaciated, and 15 (62.5%) had lost > 10% of their body weight by six months before diagnosis. At baseline, the tuberculosis group had lower serum selenium levels than did the control group. The conversion of bacteriological tests was associated with the CRP/albumin ratio and serum selenium levels 60 days after treatment initiation.

Conclusions:

Higher serum selenium levels after 60 days of treatment were associated with the conversion of bacteriological tests in pulmonary tuberculosis patients.

Coincident helminth infection modulates systemic inflammation and immune activation in active pulmonary tuberculosis

BACKGROUND

Helminth infections are known to modulate innate and adaptive immune responses in active and latent tuberculosis (TB). However, the role of helminth infections in modulating responses associated with inflammation and immune activation (reflecting disease activity and/or severity) in TB is not known.

METHODOLOGY

We measured markers of inflammation and immune activation in active pulmonary TB individuals (ATB) with co-incidental Strongyloides stercoralis (Ss) infection. These included systemic levels of acute phase proteins, matrix metalloproteinases and their endogenous inhibitors and immune activation markers. As a control, we measured the systemic levels of the same molecules in TB-uninfected individuals (NTB) with or without Ss infection.

PRINCIPAL FINDINGS

Our data confirm that ATB is associated with elevated levels of the various measured molecules when compared to those seen in NTB. Our data also reveal that co-incident Ss infection in ATB individuals is associated with significantly decreased circulating levels of acute phase proteins, matrix metalloproteinases, tissue inhibitors of matrix metalloproteinases as well as the systemic immune activation markers, sCD14 and sCD163. These changes are specific to ATB since they are absent in NTB individuals with Ss infection.

CONCLUSIONS

Our data therefore reveal a profound effect of Ss infection on the markers associated with TB disease activity and severity and indicate that co-incidental helminth infections might dampen the severity of TB disease.

Differences between pediatric extra-pulmonary and pulmonary tuberculosis: a warning sign for the future

BACKGROUND

Tuberculosis (TB) remains a major global health problem. The childhood tuberculosis has some unique features different which makes the diagnosis more complicated. Here we described the epidemiologic, clinical and microbiologic features of children with extra pulmonary and pulmonary TB.

METHODS

The data of the patients <14 years with active TB were collected and compared in pulmonary (PTB) and extrapulmonary TB (EXPTB) patients.

RESULTS

A total of 128 cases was included. Forty-two cases occurred in children were < 5 years of age; 41 cases between 6-10 years and 45 cases > 10 years. PTB was present in 75,0% of the cases, and EXPTB was present in 25% of cases. There was no significant difference between the EXPTB and PTB by means of distribution of age groups (p=0,201). The rate of patients free of constitutional symptoms were significantly higher in EXPTB compared to PTB(p=0,000). There was no significant difference between EXPTB and PTB by means of sources detection(p=0,069).

CONCLUSION

TB is still a major public health problem. EXPTB has an insidious and silent onset without any constitutional symptoms, and both microbiological confirmation and the source by an adult are not frequently found. Moreover, detection of the adult source is mandatory for controlling the TB disease in children.

Diagnostic accuracy and clinical role of rapid C-reactive protein testing in HIV-infected individuals with presumed tuberculosis in South Africa

OBJECTIVE

To determine the accuracy and role of rapid C-reactive protein (CRP) testing in human immunodeficiency virus (HIV) infected individuals with presumed tuberculosis (TB).

DESIGN

We enrolled HIV-infected adults (≥18 years)with a cough of ≥2 weeks and negative sputum smears for acid-fast bacilli in KwaZulu-Natal, South Africa. Participants were evaluated for pulmonary TB (PTB) by a nurse with rapid CRP, and independently by a physician by chest radiograph. Rapid CRP test results were compared with laboratory CRP and sputum sent for confirmation of TB.

RESULTS

Among 93 participants, 55 (59%) were female, the mean age was 35 years, and the median CD4 count was 177/mm3. Forty-five (54%) participants were diagnosed with PTB. Diagnostic sensitivity and specificity were respectively 95% (95%CI 74–99) and 51%(95%CI 35–66) for rapid CRP >8 mg/l, 87% (95%CI 73–96) and 53% (95%CI 38–68) for nurse assessment, and 69% (95%CI 52–83) and 76% (95%CI 61–87) for physician examination. Combining a negative rapid CRP(≤8 mg/l) with nurse and physician assessments reduced the post-test probability of PTB from 22% to 6% and from 32% to 6%, respectively.

CONCLUSION

Rapid CRP testing helped exclude PTB,and may be a valuable test in assisting nurses and physicians in TB-endemic regions.

Point-of-care C-reactive protein testing to facilitate implementation of isoniazid preventive therapy for people living with HIV

BACKGROUND

Symptom-based tuberculosis screening identifies less than one-third of eligible HIV-infected patients as candidates for isoniazid preventive therapy (IPT). We evaluated whether testing for C-reactive protein (CRP) improves patient selection for IPT.

METHODS

We measured CRP levels (normal <10 mg/L) using a point-of-care (POC) assay on stored serum samples from HIV-infected Ugandan adults initiating antiretroviral therapy. We assessed diagnostic accuracy in reference to baseline tuberculosis status adjudicated by an expert committee and calculated net reclassification improvement to quantify the incremental discriminatory benefit of POC-CRP in determining IPT eligibility compared to the World Health Organization (WHO) symptom screen.

RESULTS

Of 201 patients (median CD4 cell count, 137 cells/μL; interquartile range, 83-206), 5 (2.5%) had tuberculosis. Compared to the WHO symptom screen, POC-CRP had similar sensitivity (100% vs. 80%, P = 0.30) but greater specificity (21% vs. 87%, P < 0.0001) for tuberculosis. If based on the WHO symptom screen, no patients with tuberculosis but only 42 of 196 patients without tuberculosis would have been considered IPT eligible. If POC-CRP were used instead, 1 patient with tuberculosis (reclassification of cases, -20%; P = 0.32) and 129 patients without tuberculosis (reclassification of noncases, +66%; P < 0.001) would have been reclassified as IPT eligible, a net reclassification improvement of 46% (P = 0.03). In addition, POC-CRP testing would have reduced the proportion of patients without active tuberculosis requiring confirmatory tuberculosis testing (87% vs. 21%, P < 0.0001).

CONCLUSIONS

POC-CRP testing increased more than 4-fold the proportion of HIV-infected adults immediately identified as IPT eligible and decreased the proportion of patients requiring referral for further tuberculosis diagnostic testing. POC-CRP testing could substantially improve implementation of tuberculosis screening guidelines.

Heightened plasma levels of heme oxygenase-1 and tissue inhibitor of metalloproteinase-4 as well as elevated peripheral neutrophil counts are associated with TB-diabetes comorbidity

BACKGROUND

The increased prevalence of type 2 diabetes mellitus (T2DM) in countries endemic for TB poses a serious complication in the clinical management of this major infectious disease. Understanding the impact of T2DM on TB and the determinants of comorbidity is critical in responding to this growing public health problem with better therapeutic approaches. Here, we performed an exploratory study assessing a series of biologic parameters that could serve as markers of pathogenesis in TB with T2DM.

METHODS

Cross-sectional analyses of levels of heme oxygenase-1 (HO-1), acute phase proteins, tissue metalloproteinases, and tissue inhibitors of metalloproteinase (TIMPs) as well as cytokines and chemokines were performed in plasma samples from individuals with active pulmonary TB or with coincident TB and T2DM from South India.

RESULTS

Compared with patients with TB without diabetes, those with coincident T2DM exhibited increased Mycobacterium tuberculosis bacillary loads in sputum. Plasma levels of HO-1 but not of other acute phase proteins were higher in patients with TB and T2DM than in patients without diabetes, independent of bacillary sputum loads. HO-1 concentrations also positively correlated with random plasma glucose, circulating glycosylated hemoglobin, and low-density lipoprotein levels. Moreover, patients with coincident TB and T2DM exhibited increased plasma levels of TIMP-4 and elevated peripheral blood neutrophil counts, which, when considered together with HO-1, resulted in increased power to discriminate individuals with active TB with and without T2DM.

CONCLUSIONS

Elevated plasma levels of HO-1 and TIMP-4 and peripheral blood neutrophil counts are potential single and combined markers of pathogenesis in TB and T2DM.

C-reactive protein and lung diseases

C-reactive protein (CRP), a member of the pentraxin family of plasma proteins, is one of the most distinctive acute phase reactants. In response to inflammation, cell damage or tissue injury, plasma level of CRP rapidly and dramatically increases up to 1000-fold, a phenomenon that has been used for years to monitor infections and many destructive/inflammatory conditions. The magnitude of CRP increase usually correlates with the severity of injury or inflammation and reflects an important physiological role of this interesting but still under-investigated protein. It is now generally accepted that CRP is involved in host defense and inflammation. However, the exact function of this protein in health and disease remains unclear. Many studies have demonstrated that in different pathophysiological conditions CRP might be involved in the regulation of lung function and may participate in the pathogenesis of various pulmonary disorders. The fluctuation of CRP concentrations in both alveolar fluid and serum associated with different pulmonary diseases suggests its important role in lung biology. Discussion of the still controversial functions of CRP in lung physiology and diseases is the main focus of this review.

Differential expression of host biomarkers in saliva and serum samples from individuals with suspected pulmonary tuberculosis

The diagnosis of tuberculosis remains challenging in individuals with difficulty in providing good quality sputum samples such as children. Host biosignatures of inflammatory markers may be valuable in such cases, especially if they are based on more easily obtainable samples such as saliva. To explore the potential of saliva as an alternative sample in tuberculosis diagnostic/biomarker investigations, we evaluated the levels of 33 host markers in saliva samples from individuals presenting with pulmonary tuberculosis symptoms and compared them to those obtained in serum. Of the 38 individuals included in the study, tuberculosis disease was confirmed in 11 (28.9%) by sputum culture. In both the tuberculosis cases and noncases, the levels of most markers were above the minimum detectable limit in both sample types, but there was no consistent pattern regarding the ratio of markers in serum/saliva. Fractalkine, IL-17, IL-6, IL-9, MIP-1 β , CRP, VEGF, and IL-5 levels in saliva and IL-6, IL-2, SAP, and SAA levels in serum were significantly higher in tuberculosis patients (P < 0.05). These preliminary data indicate that there are significant differences in the levels of host markers expressed in saliva in comparison to those expressed in serum and that inflammatory markers in both sample types are potential diagnostic candidates for tuberculosis disease.

Diagnostic and prognostic value of serum C-reactive protein for screening for HIV-associated tuberculosis

BACKGROUND

Rapid means of ruling in or ruling out tuberculosis (TB) would permit more efficient management of patients starting antiretroviral treatment (ART).

OBJECTIVE

To assess the diagnostic and prognostic utility of C-reactive protein (CRP) among patients being screened for TB before ART in a South African ART clinic.

DESIGN

Patients were microbiologically screened for TB regardless of symptoms; serum CRP was measured, and mortality at 3 months was assessed.

RESULTS

Among 496 patients (median CD4 count 171 cells/l), culture-positive TB was diagnosed in 81 (16.3%). CRP concentrations were much higher among TB cases (median 57.8 mg/l, IQR 20.0202.7) than in those without TB (6.4 mg/l, IQR 2.121.8, P < 0.001). Very low (<1.5 mg/l) CRP concentrations excluded TB (100% negative predictive value), whereas very high concentrations (>400 mg/l) were strongly predictive of TB (100% positive predictive value). However, these thresholds encompassed only 14.3% and 2.0%, respectively, of all patients screened and identified only 12.3% of TB cases. CRP concentrations ≥50 mg/l were associated with poor prognostic characteristics, higher mycobacterial load, disseminated disease and greater mortality risk.

CONCLUSION

CRP concentrations identified groups of patients with very high or very low TB risk, but only in an unacceptably small minority of patients screened. However, in those with confirmed TB, CRP concentrations had useful prognostic value.

Circulating biomarkers of pulmonary and extrapulmonary tuberculosis in children

Tuberculosis (TB) in children is not only more likely to cause more severe disease than that seen in adults, it is also more likely to be extrapulmonary. Moreover, pediatric TB is very difficult to diagnose and suffers from a lack of understanding of host biomarkers for monitoring the progression of disease. Hence, we sought to identify the expression patterns of a variety of biomarkers in the plasma of children with pulmonary TB (PTB) and extrapulmonary TB (ETB), as well as in healthy control (HC) children. Thus, we examined a variety of circulating markers reflecting tissue inflammation, oxidative stress, innate immune activation, fibrosis, and the cytokine response. Children with active TB, compared to HC children, showed markedly elevated plasma levels of matrix metalloproteinases and their endogenous inhibitors. In addition, children with active TB had significantly elevated levels of C-reactive protein, α-2 macroglobulin, and haptoglobin, as well as hemoxygenase 1. Markers of innate immune activation (lipopolysaccharide [LPS] and lipopolysaccharide-binding protein [LBP]) were significantly lower in ETB than in PTB children. Although there were no significant differences between the two groups in their levels of cytokines (type 1 [gamma interferon (IFN-γ), tumor necrosis factor α (TNF-α), interleukin 2 (IL-2), and IL-12], type 2 [IL-4, IL-5, IL-13, and IL-33], and most type 17 [IL-17A, IL-22, IL-1β, and IL-6] and type 1 interferons [IFN-α and IFN-β]) or most of the cytokines associated with immune modulation (IL-10 and IL-20), pediatric TB was associated with elevated plasma transforming growth factor β (TGF-β), IL-21, and IL-23 levels. Thus, pediatric TB is characterized by elevated levels of a variety of biomarkers at homeostasis, suggesting that these responses may play a crucial role in disease pathogenesis.

Rapid diagnostic algorithms as a screening tool for tuberculosis: an assessor blinded cross-sectional study

BACKGROUND

A major obstacle to effectively treat and control tuberculosis is the absence of an accurate, rapid, and low-cost diagnostic tool. A new approach for the screening of patients for tuberculosis is the use of rapid diagnostic classification algorithms.

METHODS

We tested a previously published diagnostic algorithm based on four biomarkers as a screening tool for tuberculosis in a Central European patient population using an assessor-blinded cross-sectional study design. In addition, we developed an improved diagnostic classification algorithm based on a study population at a tertiary hospital in Vienna, Austria, by supervised computational statistics.

RESULTS

The diagnostic accuracy of the previously published diagnostic algorithm for our patient population consisting of 206 patients was 54% (CI: 47%-61%). An improved model was constructed using inflammation parameters and clinical information. A diagnostic accuracy of 86% (CI: 80%-90%) was demonstrated by 10-fold cross validation. An alternative model relying solely on clinical parameters exhibited a diagnostic accuracy of 85% (CI: 79%-89%).

CONCLUSION

Here we show that a rapid diagnostic algorithm based on clinical parameters is only slightly improved by inclusion of inflammation markers in our cohort. Our results also emphasize the need for validation of new diagnostic algorithms in different settings and patient populations.

Baseline predictors of sputum culture conversion in pulmonary tuberculosis: importance of cavities, smoking, time to detection and W-Beijing genotype

BACKGROUND

Time to detection (TTD) on automated liquid mycobacterial cultures is an emerging biomarker of tuberculosis outcomes. The M. tuberculosis W-Beijing genotype is spreading globally, indicating a selective advantage. There is a paucity of data on the association between baseline TTD and W-Beijing genotype and tuberculosis outcomes.

AIM

To assess baseline predictors of failure of sputum culture conversion, within the first 2 months of antitubercular therapy, in participants with pulmonary tuberculosis.

DESIGN

Between May 2005 and August 2008 we conducted a prospective cohort study of time to sputum culture conversion in ambulatory participants with first episodes of smear and culture positive pulmonary tuberculosis attending two primary care clinics in Cape Town, South Africa. Rifampicin resistance (diagnosed on phenotypic susceptibility testing) was an exclusion criterion. Sputum was collected weekly for 8 weeks for mycobacterial culture on liquid media (BACTEC MGIT 960). Due to missing data, multiple imputation was performed. Time to sputum culture conversion was analysed using a Cox-proportional hazards model. Bayesian model averaging determined the posterior effect probability for each variable.

RESULTS

113 participants were enrolled (30.1% female, 10.5% HIV-infected, 44.2% W-Beijing genotype, and 89% cavities). On Kaplan Meier analysis 50.4% of participants underwent sputum culture conversion by 8 weeks. The following baseline factors were associated with slower sputum culture conversion: TTD (adjusted hazard ratio (aHR) = 1.11, 95% CI 1.02; 1.2), lung cavities (aHR = 0.13, 95% CI 0.02; 0.95), ever smoking (aHR = 0.32, 95% CI 0.1; 1.02) and the W-Beijing genotype (aHR = 0.51, 95% CI 0.25; 1.07). On Bayesian model averaging, posterior probability effects were strong for TTD, lung cavitation and smoking and moderate for W-Beijing genotype.

CONCLUSION

We found that baseline TTD, smoking, cavities and W-Beijing genotype were associated with delayed 2 month sputum culture. Larger studies are needed to confirm the relationship between the W-Beijing genotype and sputum culture conversion.