The diagnosis of tuberculosis

QSPR analysis of distance-based structural indices for drug compounds in tuberculosis treatment

Tuberculosis (TB) is one of the most contagious diseases that has a greater mortality rate than HIV/AIDS and the cases of TB are feared to rise as a repercussion of the COVID-19 pandemic. The pharmaceutical industry is constantly looking for ways to improve drug design processes in order to combat the growth of infections and cure newly identified syndromes or genetically based dysfunctions with the help of QSPR models. QSPR models are mathematical tools that establish relationships between a molecular structure and its physicochemical attributes using structural properties. Topological indices are such properties that are generated from the molecular graph without any empirically derived measurements. This work focuses on developing a QSPR model using distance-based topological indices for anti-tuberculosis medications and their diverse physicochemical features.

The Diagnostic Value of the Thermostatic Amplification of Ribonucleic Acid in Bronchoalveolar Lavage Fluid in Smear-Negative Pulmonary Tuberculosis

Objective

This study aimed to determine the value of the simultaneous amplification and testing for Mycobacterium tuberculosis in bronchoalveolar lavage fluid (BALF) in the diagnosis of smear-negative pulmonary tuberculosis (PTB).

Methods

A total of 316 patients were selected, of which 197 had smear-negative PTB (observation group), and 119 did not have TB (control group). Bronchoscopy was performed in both groups, and BALF samples were collected for acid-fast bacilli smears, simultaneous amplification/testing for TB (SAT-TB), and BACTEC MGIT 960 cultures. The sensitivity, specificity, positive predictive, and negative predictive values of SAT-TB in BALF for the diagnosis of negative TB were calculated.

Results

The sensitivity of SAT-TB detection was 45.18%, which was significantly higher than smears and slightly lower than cultures. The specificity of SAT-TB was 99.16%, which differed slightly from the other two methods. The positive predictive value was 98.89%, which was not significantly different from the other two methods. The negative predictive value of SAT-TB was 58.91%, which was higher than smears and slightly lower than cultures.

Conclusion

The very high specificity and negative prediction of SAT-TB in BALF means that the method has great application value for the rapid diagnosis of smear-negative PTB.

Costs and cost-effectiveness of Gene Xpert compared to smear microscopy for the diagnosis of pulmonary tuberculosis using real-world data from Arsi zone, Ethiopia

Background

Early diagnosis and treatment are one of the key strategies of tuberculosis control globally, and there are strong efforts in detecting and treating tuberculosis cases in Ethiopia. Smear microscopy examination has been a routine diagnostic test for pulmonary tuberculosis diagnosis in resource-constrained settings for decades. Recently, many countries, including Ethiopia, are scaling up the use of Gene Xpert without the evaluation of the cost and cost-effectiveness implications of this strategy. Therefore, this study evaluated the cost and cost-effectiveness of Gene Xpert (MTB/RIF) and smear microscopy tests to diagnosis tuberculosis patients in Ethiopia.

Methods

We compared the costs and cost-effectiveness of tuberculosis diagnosis using smear microscopy and Gene Xpert among 1332 patients per intervention in the Arsi zone. We applied combinations of top-down and bottom-up costing approaches. The costs were estimated from the health providers’ perspective within one year (2017–2018). We employed “cases detected” as an effectiveness measure, and the incremental cost-effectiveness ratio was calculated by dividing the changes in cost and change in effectiveness. All costs and incremental cost-effectiveness ratio were reported in 2018 US$.

Results

The unit cost per test for Gene Xpert was $12.9 whereas it is $3.1 for AFB smear microscopy testing. The cost per TB case detected was $77.9 for Gene Xpert while it was $55.8 for the smear microscopy method. The cartridge kit cost accounted for 42% of the overall Gene Xpert’s costs and the cost of the reagents and consumables accounted for 41.3% ($1.3) of the unit cost for the smear microscopy method. The ICER for the Gene Xpert strategy was $20.0 per tuberculosis case detected.

Conclusion

Using Gene Xpert as a routine test instead of standard care (smear microscopy) can be potentially cost-effective. In the cost scenario analysis, the price of the cartridge, the number of tests performed per day, and the life span of the capital equipment were the drivers of the unit cost of the Gene Xpert method. Therefore, Gene Xpert can be a part of the routine TB diagnostic testing strategy in Ethiopia.

Evaluation of TB-LAMP assay for detection of Mycobacterium tuberculosis in children

BACKGROUND

Paediatric tuberculosis remains a major public health problem in developing countries. The diagnosis of tuberculosis in children is challenging because of the paucibacillary nature of the disease, due to which more sensitive nucleic acid amplification tests are needed. In this study, we determined the accuracy of WHO endorsed TB-LAMP assay for detection of Mycobacterium tuberculosis in children.

METHODS

This was a prospective study conducted between March to July, 2018. A total of 177 samples from consecutive suspected TB children were received for microbiological diagnosis of TB. All tests for Mycobacterium tuberculosis detection were performed in parallel (smear microscopy, mycobacterial culture, Xpert MTB/RIF and TB-LAMP). The diagnostic accuracy of index test i.e. TB LAMP were determined using mycobacterial culture as a reference standard.

RESULTS

Of the 177 samples, 2 (1.1%) were excluded from the study. Among 175 samples, TB-LAMP and Xpert MTB/RIF were positive in 27 (15.4%) and 25 (14.3%) samples, respectively. The sensitivity of both Xpert MTB/RIF and TB-LAMP was same, i.e. 84% (95%CI: 63.9-95.5%), when culture was considered as the reference standard. The specificity, positive predictive value and negative predictive value of TB-LAMP assay was 96% (95%CI: 91.5-98.5%), 77.8% (95%CI: 61.1-88.6%) and 97.3% (95%CI: 93.6-98.9%), respectively.

CONCLUSION

For the detection of M. tuberculosis in paediatric samples, TB-LAMP showed a sensitivity and specificity comparable to Xpert MTB/RIF.

Factors associated with differential T cell responses to antigens ESAT-6 and CFP-10 in pulmonary tuberculosis patients

The T-SPOT.TB assay detects cellular immune responses to 2 core Mycobacterium tuberculosis antigens, early secreted antigenic target of 6-kDa protein (ESAT-6) and culture filtrate protein-10 (CFP-10). T-SPOT.TB has been recently used for auxiliary diagnosis of active pulmonary tuberculosis (PTB). However, testing can produce inconsistent results due to differential PTB patient immune responses to these antigens, prompting us to identify factors underlying inconsistent results.Data were retrospectively analyzed from 1225 confirmed PTB patients who underwent T-SPOT.TB testing at 5 specialized tuberculosis hospitals in China between December 2012 and November 2015. Numbers of spot-forming cells (SFCs) reflecting T cell responses to ESAT-6 and CFP-10 antigens were recorded then analyzed via multivariable logistic regression to reveal factors underlying discordant T cell responses to these antigens.The agreement rate of 84.98% (82.85%-86.94%) between PTB patient ESAT-6 and CFP-10 responses demonstrated high concordance. Additionally, positivity rates were higher for ESAT-6 than for CFP-10 (84.8% vs 80.7%, P < .001), with ESAT-6 and CFP-10 microwell SFC numbers for each single positive group not differing significantly (P > .99), while spot numbers of the single positive group were lower than numbers for the double positive group (P < .001). Elderly patients (aged ≥66 years) and patients receiving retreatment were most likely to have discordance results.ESAT-6 promoted significantly more positive T-SPOT.TB results than did CFP-10 in PTB patients. Advanced age and retreatment status were correlated with discordant ESAT-6 and CFP-10 results. Assessment of factors underlying discordance may lead to improved PTB diagnosis using T-SPOT.TB.

Mycoplasma pneumoniae infection mimicking tuberculous pleurisy in a young woman: a case report and literature review

A 30-year-old woman was admitted to a different hospital with a 2-day history of fever, cough, and expectoration. She had a history of left pulmonary tuberculosis 8 years previously. Chest computed tomography showed an infiltrate in the inferior lobe of the left lung and spot-like calcifications in the anterior lobe of the upper left lobe and lower lobe of the left lung. After antibacterial treatment, the patient’s condition deteriorated and she developed significant pleural effusion on the left side. The pleural effusion assay showed a lymphocyte-predominant exudate with a significantly increased adenosine deaminase level. The patient was transferred to our hospital with a suspected diagnosis of tuberculous pleuritis. A serum test for Mycoplasma pneumoniae-specific immunoglobulin M was positive. Because of the limitations of this test in determining the occurrence of recent infection, a thoracoscopic pleural biopsy was performed, and M. pneumoniae DNA was detected in the biopsy tissue using M. pneumoniae-specific polymerase chain reaction. Thus, the patient was diagnosed with M. pneumoniae-related parapneumonic effusion. Clinicians must be aware of the usefulness and limitations of a high adenosine deaminase level and know that lymphocyte predominance in pleural effusion does not always indicate tuberculous pleurisy, especially in areas of high tuberculosis prevalence.

Lab-on-a-Film disposable for genotyping multidrug-resistant Mycobacterium tuberculosis from sputum extracts

We describe a Lab-on-a-Film disposable that detects multidrug-resistant tuberculosis (MDR-TB) from sputum extracts. The Lab-on-a-Film disposable consists of 203 gel elements that include DNA sequences (probes) for 37 mutations, deletions, or insertion elements across 5 genes (including an internal control). These gel elements are printed on a flexible film, which costs approximately 500 times less than microarray glass. The film with printed gel elements is then laminated to additional rollable materials (films) to form a microfluidic flow cell. We combined multiplex amplification and hybridization steps in a single microfluidic chamber, without buffer exchanges or other manipulations up to and throughout hybridization. This flow cell also incorporates post hybridization wash steps while retaining an entirely closed-amplicon system, thus minimizing the potential for sample or amplicon cross-contamination. We report analytical sensitivity of 32 cfu mL-1 across all MDR-TB markers and detection of MDR-TB positive clinical specimens using an automated TruTip workstation for extraction and the Lab-on-a-Film disposable for amplification and detection of the extracts.

Characteristics of peripheral Vγ2Vδ2 T cells in interferon-γ release assay negative pulmonary tuberculosis patients

Background

It is not fully explained why some active tuberculosis patients show negative interferon-γ release assays (IGRAs). In this study, we tried to explore associations of IGRAs with the characteristics of peripheral Vγ2Vδ2 T cells and their functions of producing cytokines.

Methods

32 pulmonary tuberculosis patients were enrolled and divided into two groups according to their IGRAs results: 16 with IGRA-negative as test group and 16 with IGRA-positive as control group. Chest X-rays and T-SPOT.TB tests were performed and the severity of the lung lesions was scored. The amount of Vγ2Vδ2T cell and their expression levels of the apoptosis-related membrane surface molecule Fas and FasL in peripheral blood were analyzed by flow cytometry, and the function of secreting cytokines (IFN-γ, TNF-α and IL-17A) of Vγ2Vδ2 T cell were determined by intracellular cytokine staining.

Results

The IGRA-negative TB patients had more lesion severity scores and displayed reduced peripheral blood Vγ2Vδ2 T cell counts (p = 0.009) as well as higher Fas and FasL expression in peripheral blood Vγ2Vδ2 T cells (p = 0.043, 0.026). A high lesion severity score was correlated with a decreased Vδ2+ T cell number and increased Vγ2Vδ2 T cells Fas/FasL expression leve in the peripheral blood (p = 0.00, P < 0.01). The function of secreting cytokines was slightly impaired in IGRA-negative TB patients (p = 0.402). There is no significant differences in expression levels of Fas and FasL in CD4+ T cells (p = 0.224, 0.287) or CD8+ T cells (p = 0.184, 0.067) between test and control groups.

Conclusion

Compared with IGRA-positive TB patients, the IGRA-negative TB patients had more lesion severity scores, the number of Vγ2Vδ2 T cells decreased and the function of secreting cytokines impaired. In addition, we suggest that increased expression of Fas/FasL triggers Vγ2Vδ2 T cell apoptosis.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3328-x) contains supplementary material, which is available to authorized users.

Label-Free Quantitative Proteomics Identifies Novel Plasma Biomarkers for Distinguishing Pulmonary Tuberculosis and Latent Infection

The lack of effective differential diagnostic methods for active tuberculosis (TB) and latent infection (LTBI) is still an obstacle for TB control. Furthermore, the molecular mechanism behind the progression from LTBI to active TB has been not elucidated. Therefore, we performed label-free quantitative proteomics to identify plasma biomarkers for discriminating pulmonary TB (PTB) from LTBI. A total of 31 overlapping proteins with significant difference in expression level were identified in PTB patients (n = 15), compared with LTBI individuals (n = 15) and healthy controls (HCs, n = 15). Eight differentially expressed proteins were verified using western blot analysis, which was 100% consistent with the proteomics results. Statistically significant differences of six proteins were further validated in the PTB group compared with the LTBI and HC groups in the training set (n = 240), using ELISA. Classification and regression tree (CART) analysis was employed to determine the ideal protein combination for discriminating PTB from LTBI and HC. A diagnostic model consisting of alpha-1-antichymotrypsin (ACT), alpha-1-acid glycoprotein 1 (AGP1), and E-cadherin (CDH1) was established and presented a sensitivity of 81.2% (69/85) and a specificity of 95.2% (80/84) in discriminating PTB from LTBI, and a sensitivity of 81.2% (69/85) and a specificity of 90.1% (64/81) in discriminating PTB from HCs. Additional validation was performed by evaluating the diagnostic model in blind testing set (n = 113), which yielded a sensitivity of 75.0% (21/28) and specificity of 96.1% (25/26) in PTB vs. LTBI, 75.0% (21/28) and 92.3% (24/26) in PTB vs. HCs, and 75.0% (21/28) and 81.8% (27/33) in PTB vs. lung cancer (LC), respectively. This study obtained the plasma proteomic profiles of different M.TB infection statuses, which contribute to a better understanding of the pathogenesis involved in the transition from latent infection to TB activation and provide new potential diagnostic biomarkers for distinguishing PTB and LTBI.

Prospective Comparison of QFT-GIT and T-SPOT.TB Assays for Diagnosis of Active Tuberculosis

T-SPOT.TB and QuantiFERON-TB Gold In-Tube (QFT-GIT) tests, as two commercial blood assays for diagnosing active tuberculosis (ATB), are not yet fully validated. Especially, there are no reports on comparing the efficacy between the two tests in the same population in China. A multicenter, prospective comparison study was undertaken at four hospitals specializing in pulmonary diseases. A total of 746 suspected pulmonary TB were enrolled and categorized, including 185 confirmed TB, 298 probable TB and 263 non-TB. Of 32 patients with indeterminate test results (ITRs), age and underlying disease were associated with the rate of ITRs. Furthermore, the rate of ITRs determined by T-SPOT.TB was lower than QFT-GIT (0.4% vs. 4.3%, P < 0.01). When excluding ITRs, the sensitivities of T-SPOT.TB and QFT-GIT were 85.2% and 84.8%, and specificities of 63.4% and 60.5%, respectively in the diagnosis of ATB. The two assays have an overall agreement of 92.3%, but exhibited a poor linear correlation (r² = 0.086) between the levels of interferon-γ release detected by the different assays. Although having some heterogeneity in detecting interferon-γ release, both the QFT-GIT and T-SPOT.TB demonstrated high concordance in diagnosing ATB. However, neither of them showed suitability in the definitive diagnosis of the disease.

Development and application of a rapid Mycobacterium tuberculosis detection technique using polymerase spiral reaction

Mycobacterium tuberculosis is an age-old bacterium that is difficult to eliminate. A simple and rapid diagnostic method is of great importance to prevent the spread of M. tuberculosis. Here, we developed a low-cost rapid M. tuberculosis nucleic acid detection technique, named GenePop, which enabled the storage and transport of M. tuberculosis diagnostic reagent at ambient temperatures, without the need for professional operations or expensive instrumentation. Using a vitrification method, we vitrified heat-unstable components onto the cap of a reaction tube, and placed heat-stable components at the bottom of the reaction tube by sealing them with paraffin wax. The all-in-one detection tube, when used together with our other invention—a multi-functional sample treatment tube pre-filled with a nucleic acid-releasing agent—only required three simple steps to yield results. A comparative analysis with a commercial qPCR kit for M. tuberculosis indicated that our new technique had a concordance rate of 91.6%, showing no cross-reactivity with 11 other bacteria. The complete operation time was only 65 min. It is suitable for use in field settings or by personnel in grass-root units, and is applicable in household activities, hence can be used in developing countries.

CTL immunogenicity of Rv3615c antigen and diagnostic performances of an ESAT-6/CFP-10/Rv3615c antigen cocktail for Mycobacterium tuberculosis infection

T cell immune responses have played pivotal roles in host immune protection against Mycobacterium tuberculosis (MTB) infection. MTB specific antigen, Rv3615c (EspC), was identified to be as immunodominant as the well-known ESAT-6 and CFP-10, and has brought promising expectations to more sensitive T-cell based diagnosis and vaccine development. However, limited knowledge about the immunogenicity and diagnostic values of this antigen has restricted its application in clinical practice. Herein, the Rv3615c antigen was identified as a robust CTL immunoantigen with broadly cross-human leucocyte antigen (HLA) allele recognized peptides which may contribute to the broad recognition of Rv3615c antigen among the population. A three-antigen-cocktail (3-Ag-cocktail) comprising of ESAT-6, CFP-10 and Rv3615c was investigated in a multicenter, randomized and double-blinded study to evaluate its clinical diagnostic performances. A significantly improved sensitivity was demonstrated against the 3-Ag-cocktail compared with that against ESAT-6 and CFP-10. Both responsive magnitude and sensitivity were significantly lower in patients concurrently suffering from cancer, indicating its restriction in diagnosis of immunocomprised patients. In conclusion, inclusion of the Rv3615c antigen with multiple HLA restricted CTL epitopes would benefit the T-cell based diagnosis of MTB infection.

Performance of interferon-γ release assay in the diagnosis of tuberculous lymphadenitis: a meta-analysis

Background

The diagnostic values of interferon-gamma release assays (IGRA) in tuberculosis (TB) vary a lot with different site of infections, with especially higher sensitivities in chronic forms of TB such as tuberculosis of the lymph node. We conducted a meta-analysis to comprehensively evaluate the overall accuracy of diagnostic IGRA for tuberculous lymphadenitis.

Methods

Pubmed, Web of Science, EMBASE, Wanfang and CNKI databases up to February 17, 2017 were searched to identify published studies. The study quality was evaluated using the QUADAS-2 checklist. The pooled estimates of diagnostic parameters were generated using a bivariate random-effects model and summary receiver operating characteristic (SROC) curves were used to summarize global performance.

Results

A total of ten qualified studies, performed in Korea or China, including 1,084 patients, were enrolled in this meta-analysis. The pooled estimates of diagnostic accuracy were as follows: sensitivity, 0.89 (95% CI [0.85–0.92]); specificity, 0.81 (95% CI [0.77–0.83]); positive likelihood ratio (PLR), 4.25 (95% CI [2.79–6.47]); negative likelihood ratio (NLR), 0.16 (95% CI [0.12–0.22]); and area under the curve (AUC) was 0.93. According to subgroup analyses, studies conducted using QuantiFERON-TB, in Korean population and focusing on cervical lymphadenitis exhibited relative higher specificity while lower sensitivity. No evidence of publication bias was identified.

Conclusions

IGRA exhibits high diagnostic accuracy in tuberculous lymphadenitis. The diagnostic value of IGRA differed by different IGRA methods, ethnicity and lymphadenitis location. Our conclusion may be more applicable to population from TB prevalent areas.

Establishment of Elevated Serum Levels of IL-10, IL-8 and TNF-β as Potential Peripheral Blood Biomarkers in Tubercular Lymphadenitis: A Prospective Observational Cohort Study

Background

Tubercular lymphadenitis (TL) is the most common form of extra-pulmonary tuberculosis (TB) consisting about 15–20% of all TB cases. The currently available diagnostic modalities for (TL), are invasive and involve a high index of suspicion, having limited accuracy. We hypothesized that TL would have a distinct cytokine signature that would distinguish it from pulmonary TB (PTB), peripheral tubercular lymphadenopathy (LNTB), healthy controls (HC), other lymphadenopathies (LAP) and cancerous LAP. To assess this twelve cytokines (Tumor Necrosis Factor (TNF)—α, Interferon (IFN) -γ, Interleukin (IL)-2, IL-12, IL-18, IL-1β, IL-10, IL-6, IL-4, IL-1Receptor antagonist (IL-1Ra), IL-8 and TNF-β, which have a role in pathogenesis of tuberculosis, were tested as potential peripheral blood biomarkers to aid the diagnosis of TL when routine investigations prove to be of limited value.

Methods and Findings

A prospective observational cohort study carried out during 2010–2013. This was a multi-center study with three participating hospitals in Delhi, India where through random sampling cohorts were established. The subjects were above 15 years of age, HIV-negative with no predisposing ailments to TB (n = 338). The discovery cohort (n = 218) had LNTB (n = 50), PTB (n = 84) and HC (n = 84). The independent validation cohort (n = 120) composed of patients with cancerous LAP (n = 35), other LAP (n = 20) as well as with independent PTB (n = 30), LNTB (n = 15) and HC (n = 20). Eight out of twelve cytokines achieved statistical relevance upon evaluation by pairwise and ROC analysis. Further, variable selection using random forest backward elimination revealed six serum biosignatures including IL-12, IL-4, IL-6, IL-10, IL-8 and TNF-β as optimal for classifying the LNTB status of an individual. For the sake of clinical applicability we further selected a three analyte panel (IL-8, IL-10 and TNF-β) which was subjected to multinomial modeling in the independent validation cohort which was randomised into training and test cohorts, achieving an overwhelming 95.9% overall classifying accuracy for correctly classifying LNTB cases with a minimal (7%) misclassification error rate in the test cohort.

Conclusions

In our study, a three analyte serum biosignatures and probability equations were established which can guide the physician in their clinical decision making and step wise management of LNTB patients. This set of biomarkers has the potential to be a valuable adjunct to the diagnosis of TL in cases where AFB positivity and granulomatous findings elude the clinician.

Utility of QuantiFERON-TB Gold In-Tube assay in adult, pulmonary and extrapulmonary, active tuberculosis diagnosis

BACKGROUND

Tuberculosis remains a public health problem in France and the diagnosis of tuberculosis disease (TB) is sometimes difficult. The aim of this study was to analyse the contribution of the QuantiFERON-TB Gold In-Tube assay (QFT-GIT) to TB diagnosis.

METHODS

Sixty patients hospitalized with TB, for whom a QFT-GIT assay had been performed between June 2008 and June 2011 at the University Hospital of Bondy in the north-east of Paris, were identified retrospectively. Clinical and laboratory data were collected. The sensitivity, specificity, predictive values, and likelihood ratios of the QFT-GIT were all calculated. Furthermore, the characteristics of patients testing positive were compared to those of patients testing negative, as well as the QFT-GIT values according to several different factors.

RESULTS

The sensitivity of the QFT-GIT was 85% (95% confidence interval (CI) 0.73-0.92) and specificity was 73.3% (95% CI 0.68-0.78). The positive predictive value was 39.5% and the negative predictive value was 97.3%. The positive and negative likelihood ratios were 3.2 and 0.20, respectively. The prevalence of TB in this population was 15% (pre-test probability). After a positive test result, the probability of TB increased to 40% (post-positive probability test); after a negative test result, it decreased to 4.5% (post-negative probability test). The combination of the QFT-GIT test with the tuberculin skin test brought no significant improvement in sensitivity. Factors significantly associated with a negative QFT-GIT result included older age, high C-reactive protein, a low lymphocyte count, and immunosuppressant intake. The test value in quantitative terms was significantly higher in those with lymph node TB than in those with pulmonary TB, and in younger patients (<40 years) than in older patients (>40 years old).

CONCLUSION

On its own, QFT-GIT is an insufficient tool to confirm the diagnosis of TB disease. However, it may form part of an ensemble of tools in combination with clinical, biological, and radiological assessments.

Tuberculine reaction measured by infrared thermography

SETTING

The infection with Mycobacterium tuberculosis gives a delayed immune response, measured by the tuberculine skin test. We present a new technique for evaluation based on automatic detection and measurement of skin temperature due to infrared emission.

DESIGN

34 subjects (46.8±16.9 years) (12/22, M/F) with suspected tuberculosis disease were examined with an IR thermal camera, 48 h after tuberculin skin injection.

RESULTS

In 20 subjects, IR analysis was positive for tuberculine test. Mean temperature of injection area was higher, around 1°C, for the positive group (36.2±1.1°C positive group; 35.1±1.6°C negative group, p<0.02 T test for unpaired groups).

CONCLUSION

IR image analysis achieves similar estimation of tuberculin reaction as the visual evaluation, based on higher temperature due to increased heat radiation from the skin lesion.

Detection of Mycobacterium tuberculosis complex in sputum specimens using a loop-mediated isothermal amplification assay in Korea

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis complex (MTC), remains one of the leading causes of death in the world. In Korea, the current prevalence of multidrug-resistant TB (MDR-TB) poses a major problem. The most common method for diagnosing TB in developing countries is sputum smear microscopy; however, the sensitivity of this test is relatively low and it usually requires well-trained laboratory staff. Cultures of MTC require up to several weeks in sophisticated facilities, such as Biosafety Level 3. Effective diagnostic techniques are necessary to control TB. In Korea, we evaluated a loop-mediated isothermal amplification (LAMP) assay targeting the hspX gene (TB-hspX-LAMP) of MTC. For clinical evaluation, culture confirmation, smear microscopy and TB-hspX-LAMP were performed on 303 sputum specimens obtained from suspected TB patients in Korea. The sensitivity, specificity, positive predictive value and negative predictive value of TB-hspX-LAMP were 71.1, 98.8, 91.4 and 95.1%, respectively, compared with TB culture, which is the gold standard for diagnosis of TB. In contrast, the comparable values of smear microscopy were 24.4, 98.1, 68.8 and 88.2%, respectively. Therefore, we concluded that TB-hspX-LAMP was superior to the use of smear microscopy for the detection of MTC in sputum specimens in clinical settings in Korea.

The efficacy of the interferon-γ release assay for diagnosing cervical tuberculous lymphadenitis: A prospective controlled study

OBJECTIVES/HYPOTHESIS

The whole-blood interferon (IFN)-γ release assay (IGRA) has been studied mainly for diagnosing latent tuberculosis (TB). We prospectively evaluated its diagnostic usefulness in patients with suspected cervical TB lymphadenitis.

STUDY DESIGN

Prospective cohort study.

METHODS

An IGRA was performed in subjects with suspected TB lymphadenitis. To evaluate the diagnostic performance of the IGRA, we calculated the sensitivity and specificity of culture, radiologic imaging, polymerase chain reaction testing, fine needle aspiration, and excisional biopsy.

RESULT

Of the 271 adult patients with suspected TB lymphadenitis, 42 were diagnosed with the disease. The overall sensitivity and specificity of the IGRA were 78.8% and 95.5%, respectively. When the cutoff value of IFN-γ was set to 0.26 IU/mL, it met the inclusion criteria for suspicious TB lymphadenitis, with sensitivity and specificity of 83.3% and 95.1%, respectively.

CONCLUSIONS

The IGRA is useful in diagnosing TB lymphadenitis, with high sensitivity and specificity.

LEVEL OF EVIDENCE

4.

Diagnostic value of T-SPOT.TB interferon-γ release assays for active tuberculosis

The aim of the present study was to evaluate the diagnostic value of interferon-γ release assays for the detection of active tuberculosis (ATB) in patients previously vaccinated with Bacillus Calmette-Guérin (BCG). In total, 540 patients underwent the T-SPOT.TB test, including 295 patients with active pulmonary TB (PTB), 52 patients with active extrapulmonary TB (EPTB), 11 individuals with inactive TB and 182 non-TB cases. Simultaneously, 186 patients with ATB, including PTB and EPTB cases, and 125 non-TB patients underwent tuberculin skin tests (TST). Associations between the sensitivity of the T-SPOT.TB assays and lung lesion severity, positive smear grade, disease site and the duration of anti-TB treatment were evaluated. The sensitivity and specificity values of the T-SPOT.TB assay for diagnosing ATB were 76.66 and 76.37%, respectively, and the positive rate in the inactive TB test results was significantly lower (23.63%; P<0.001). The diagnostic sensitivity was higher in the PTB cases when compared with the EPTB cases (P=0.01). Furthermore, the diagnostic sensitivity of the ATB cases undergoing anti-TB treatment was significantly lower when compared with the cases not undergoing treatment (P=0.002), and the sensitivity gradually decreased with the treatment duration (P=0.01). In addition, a statistically significant difference was identified in the specificity between the T-SPOT.TB assay and the TST (76.37 vs. 51.15%; P<0.001), whereas the sensitivity values did not differ significantly (76.66 vs. 75.56%). Therefore, the results indicated that the T-SPOT.TB assay is a promising diagnostic test for active PTB in a BCG-vaccinated population, and should replace the TST. As the administration of anti-TB treatment resulted in a lower sensitivity to the diagnostic test, the T-SPOT.TB assay may also be suitable for the assessment of treatment outcomes.

Towards tuberculosis elimination: an action framework for low-incidence countries

This paper describes an action framework for countries with low tuberculosis (TB) incidence (<100 TB cases per million population) that are striving for TB elimination. The framework sets out priority interventions required for these countries to progress first towards "pre-elimination" (<10 cases per million) and eventually the elimination of TB as a public health problem (less than one case per million). TB epidemiology in most low-incidence countries is characterised by a low rate of transmission in the general population, occasional outbreaks, a majority of TB cases generated from progression of latent TB infection (LTBI) rather than local transmission, concentration to certain vulnerable and hard-to-reach risk groups, and challenges posed by cross-border migration. Common health system challenges are that political commitment, funding, clinical expertise and general awareness of TB diminishes as TB incidence falls. The framework presents a tailored response to these challenges, grouped into eight priority action areas: 1) ensure political commitment, funding and stewardship for planning and essential services; 2) address the most vulnerable and hard-to-reach groups; 3) address special needs of migrants and cross-border issues; 4) undertake screening for active TB and LTBI in TB contacts and selected high-risk groups, and provide appropriate treatment; 5) optimise the prevention and care of drug-resistant TB; 6) ensure continued surveillance, programme monitoring and evaluation and case-based data management; 7) invest in research and new tools; and 8) support global TB prevention, care and control. The overall approach needs to be multisectorial, focusing on equitable access to high-quality diagnosis and care, and on addressing the social determinants of TB. Because of increasing globalisation and population mobility, the response needs to have both national and global dimensions.

Identification of whole pathogenic cells by monoclonal antibodies generated against a specific peptide from an immunogenic cell wall protein

We selected the immunogenic cell wall ß-(1,3)-glucosyltransferase Bgl2p from Candida albicans as a target protein for the production of antibodies. We identified a unique peptide sequence in the protein and generated monoclonal anti- C. albicans Bgl2p antibodies, which bound in particular to whole C. albicans cells.

Prevalence of national treatment algorithm defined smear positive pulmonary tuberculosis in HIV positive patients in Brazzaville, Republic of Congo

Background

In the Republic in Congo, the national algorithm for the diagnosis of pulmonary tuberculosis (TB) relies on Ziehl-Neelsen (ZN) sputum smear microscopy, chest X-ray radiography (CXR) and clinical symptoms. Microscopy positive pulmonary TB (MPT+) is defined as symptoms of TB and a positive ZN smear. Microscopy negative pulmonary TB (MPT-) is defined as symptoms of TB, a negative ZN smear but CXR changes consistent with TB. The present cross-sectional study was designed to determine the prevalence of positive and negative MPT individuals among HIV positive and HIV negative individuals presenting to an ambulatory TB treatment center (CTA) in Brazzaville.

Methods

All study participants underwent a physical examination, chest radiography and three ZN sputum smear examinations and HIV testing. Viral load and CD4 counts were determined for HIV positive individuals.

Results

775 individuals presented with symptoms of TB. 425 individuals accepted the voluntary HIV test. 133 (31.3%) were HIV positive (HIV+) and 292 (68.7%) were HIV negative (HIV-). Of the 292 HIV- individuals 167 (57%) were classified as positive MPT and 125 (43%) as negative MPT. Of the 133 HIV positive individuals 39 (29%) were classified as MPT + and 94 (71%) as MPT-.

Conclusion

Our study shows that the prevalence of positive MPT individuals is lower among HIV positive individuals compared to HIV negative individuals in agreement to reports from other countries. The data suggest that a substantial number of HIV positive pulmonary TB cases are not detected by the national algorithm and highlight the need for new diagnostic tests in this population.

Evaluation of in-house loop-mediated isothermal amplification (LAMP) assay for rapid diagnosis of M. tuberculosis in pulmonary specimens

BACKGROUND

Loop-mediated isothermal amplification (LAMP) assay has come forward as a rapid, cost-effective molecular technique for diagnosis of tuberculosis (TB) in developing countries. This study evaluated Mycobacterium tuberculosis-specific in-house LAMP assay targeting 16s rRNA and compared it with other conventional tests and nucleic acid amplification assay (IS6110 PCR).

METHODS

A total of 133 sputum specimens (103 from suspected pulmonary TB cases and 30 from non-TB controls) were subjected to conventional tests, IS6110 PCR and 16s rRNA LAMP assay.

RESULTS

Of the 103 patients, the maximum number of cases were found to be positive by LAMP assay, that is, in 87 (84.5%) patients, followed by culture positive in 78 (75.7%), IS6110 PCR in 74 (71.8%), and smear positive in 70 (67.9%) patients. Of the 83 smear positive and/or culture positive cases, LAMP detected 77 (92.77%) cases, and was found to be superior to IS6110 PCR, which could detect 69 (83.1%) cases; a concordance of 0.6 was obtained between the two tests using kappa statistics.

CONCLUSION

Overall, LAMP was simple and efficacious for early diagnosis of smear positive, culture positive cases as well as for confirmation of smear negative, culture negative cases, and was found to be superior to IS6110 PCR.

Evaluation of GeneXpert MTB/RIF for the detection of Mycobacterium tuberculosis and resistance to rifampin in clinical specimens

OBJECTIVES

GeneXpert (GX) is a novel real-time polymerase chain reaction assay for the simultaneous detection of Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF). We evaluated the performance of GX for direct detection of MTB in respiratory and non-respiratory specimens and assessed the ability of the assay to detect resistance to RIF in non-tuberculosis (TB) endemic country.

METHODS

We analyzed 595 clinical samples in a 1550-bed tertiary hospital in Madrid, Spain. Specimens were processed using GX, auramine smear, conventional culture, and drug phenotypic susceptibility testing (DST) with MGIT SIRE (BD).

RESULTS

Of the 595 clinical samples, 305 (51.3%) were non-respiratory and 290 (48.7%) were respiratory. In total, MTB was isolated in 81 specimens, 71 of which were positive with GX. The sensitivity, specificity, PPV, and NPV of the GX were: 97.1%, 98.6%, 95.7% and 99.1% for respiratory samples and 33.3%, 99.7%, 80.0% and 97.3% for non-respiratory. GX detected 8 RIF-resistant samples, but only 5 were confirmed by DST.

CONCLUSIONS

GX is an accurate, easy-to-apply and rapid test to detect MTB, especially in smear-positive respiratory samples. Although is a useful tool for the rapid identification of RIF-resistant MTB strains, the rifampin resistant results should be confirmed by DST.

Tuberculosis, drug use and HIV infection in Central Asia: an urgent need for attention

INTRODUCTION

Rates of tuberculosis in Central Asia are extremely high, and even more alarming are the very high rates of multidrug-resistant tuberculosis (MDR-TB) in Kazakhstan, Uzbekistan, Tajikistan and Kyrgyzstan. In addition, rates of HIV infection related to injection drug use seems to be rising as well, thus creating conditions for a potentially devastating co-epidemic of TB/HIV and MDR-TB/HIV which would have terrible consequences for public health in these countries.

CURRENT STATUS

In many countries of Central Asia, diagnosis of tuberculosis still rests on clinical grounds or simple technologies such as chest radiograph and sputum smear examination. Modern molecular techniques such as GenExpert are being introduced in Kazakhstan and Uzbekistan, and perhaps soon in Kyrgyzstan. Treatment of TB is still often centered around prolonged inpatient stay at TB hospitals. Only a minority of patients with HIV infection are receiving ART, and TB and HIV services are not well integrated. Needle exchange programs are becoming increasingly available, but opioid substitution therapy is rarely used in Central Asia. TB, drug treatment and HIV services are generally not well-integrated.

CONCLUSIONS

To combat this developing storm, integration of TB services, HIV care, and substance abuse treatment programs is needed urgently to allow efficient and effective diagnosis and treatment of these conditions in a coordinated manner.

Community-acquired pneumonia and tuberculosis: differential diagnosis and the use of fluoroquinolones

The respiratory fluoroquinolones moxifloxacin, gemifloxacin, and high-dose levofloxacin are recommended in guidelines for effective empirical antimicrobial therapy of community-acquired pneumonia (CAP). The use of these antibiotics for this indication in areas with a high prevalence of tuberculosis (TB) has been questioned due to the perception that they contribute both to delays in the diagnosis of pulmonary TB and to the emergence of fluoroquinolone-resistant strains of Mycobacterium tuberculosis. In this review, we consider some of the important questions regarding the potential use of fluoroquinolones for the treatment of CAP where the burden of TB is high. The evidence suggests that the use of fluoroquinolones as recommended for 5-10 days as empirical treatment for CAP, according to current clinical management guidelines, is appropriate even in TB-endemic regions. It is critical to quickly exclude M. tuberculosis as a cause of CAP using the most rapid relevant diagnostic investigations in the management of all patients with CAP.

Statistical Evaluation of Two Microbiological Diagnostic Methods of Pulmonary Tuberculosis After Implementation of a Directly Observed Treatment Short-course Program

OBJECTIVES

To evaluate the diagnostic accuracy of smear and culture tests of clinical samples of pulmonary tuberculosis after the introduction of the directly observed treatment short-course (DOTS) program.

METHODS

Using sputum samples from 572 individuals as a self-selected population, both Ziehl-Neelsen staining and culturing on Lowenstein-Jensen medium were carried out as diagnostic procedures. Using Bayes' rule, the obtained data set was analyzed.

RESULTS

Of the 572 samples, 33 (0.05769) were true positive (results of both tests positive) cases; 22 samples (0.03846) were false positive (smear test positive and culture test negative) cases; 62 samples (0.10839) were false negative (smear test negative and culture test positive) cases; and 455 samples (0.79545) were true negative (results of both tests negative) cases. Values of test statistics, sensitivity, and specificity were used to compute several inherent other Bayesian test statistics. The a priori probability or prevalence value of tuberculosis in the targeted population was 0.166. The a posteriori probability value computed arithmetically was 0.6614 and that obtained by the graphical method was 0.62.

CONCLUSIONS

The smear test was found to be dependable for 95.4% with stable TB infections, and it was not dependable for 34.7% without stable TB infections. The culture test could be regarded as the gold standard for 96.15% as seen with the data set, which was obtained after the implementation of the DOTS program.

Of parasites and men

The living world has evolved and is evolving through interspecific relationships between organisms. The diversity of these interactions is enormous going from mutualism to parasitism. Humans live with a multitude of microorganisms, essential for their biology. However, interactions are not always advantageous. Indeed, many organisms might become pathogens, such as the Plasmodium species, the causative agents of malaria. Like many other microorganisms, they are «Machiavellian» in their capacity to elaborate a range of reproduction strategies, giving them a huge advantage in terms of adaptation. Here, we discuss the role played by parasites in the ecology and evolution of living organisms and particularly of humans. In the study of infectious diseases, humans are legitimately the focal point, although they represent only one ecosystem among many others and not taking this into account certainly biases our global view of the system. Indeed, we know only a minimal fraction of the microorganisms we live with. However, parasites have shaped and are still shaping the human genome. Several genetic signatures are the proofs of the selection pressures by parasites that humankind has endured during its evolution. But, ultimately, what are the solutionsfor living with pathogens? Should we eradicate them or should we learn how to control and manage them?

The role of induced sputum in the diagnosis of pulmonary tuberculosis

BACKGROUND

Microbiological confirmation of pulmonary tuberculosis (TB) is of paramount importance in the era of immunocompromised host and emergence of multi-drug resistance.

OBJECTIVES

To assess the value of sputum induction (SI) with hypertonic saline nebulization as a diagnostic tool in patients with suspected pulmonary TB who have no/inadequate sputum or have a sputum smear negative for acid fast bacillus (AFB).

MATERIALS AND METHODS

One hundred patients with clinical and radiological evidence of pulmonary TB with no/inadequate sputum or smear negative with spontaneous sputum were studied. Sputum was induced with 20 mL of 3% hypertonic saline solution delivered through ultrasonic nebulizer. The specimens were subjected to Ziehl Neelsen staining and were examined under oil immersion lens for the presence of AFB. The specimens were also subjected to mycobacterial culture in BACTEC 460 TB system.

RESULTS

Ninety five patients could produce adequate sputum after SI. Sputum from thirty two patients were found to be positive both in smear and culture while sputum from another three patients were smear negative, but culture positive.

CONCLUSION

SI is a safe, cheap and non-invasive procedure and provides significant yield in the diagnosis of pulmonary TB; thus, increasing the case detection rate of smear positive pulmonary TB.

Evaluation of interferon-γ release assay in the diagnosis of osteoarticular tuberculosis

The aim of this study was to assess the value of interferon-γ (IFN-γ) release assay (IGRA) (T-SPOT.TB) for patients with suspected osteoarticular tuberculosis (TB) in comparison with conventional and molecular methods. Of 145 patients with suspected osteoarticular TB, recruited from Beijing Chest Hospital between July 2011 and June 2012, 86 (59.3%)had osteoarticular TB (26 with culture-confirmed TB, 60 with probable TB), 24 (16.6%) were not having active TB. The remaining 17 (11.7%) inconclusive TB and 18 (12.4%) possible TB were excluded from final analysis. In addition to conventional tests and molecular method, T-SPOT.TB assay using peripheral blood mononuclear cells to examine IFN-γ response to early secretory antigenic target 6 and culture filtrate protein 10 was also performed. The sensitivity and specificity for T-SPOT.TB assay were 94.2% and 70.8%, respectively. A statistically significant difference in sensitivity was found between T-SPOT.TB assay (94.2%) and other tests (acid-fast bacilli smear (19.7%), culture (34.2%), real-time PCR (36.8%); P < 0.01, respectively). These results suggested that the IGRA assay could provide useful aids in the diagnosis of osteoarticular TB.

Association of polymorphisms in the Chr18q11.2 locus with tuberculosis in Chinese population

A GWAS study has reported that two single nucleotide polymorphisms (SNPs) were associated with predisposition to tuberculosis (TB) in African populations. These two loci represented the long-waited GWAS hits for TB susceptibility. To determine whether these two SNPs are associated with TB in Chinese population, we attempted an replication in a cohort of over one thousand Chinese TB patients and 1,280 healthy controls using melting temperature shift allele-specific genotyping analysis. We found that only SNP rs4331426 was significantly associated with TB in Chinese population (p = 0.011). However, the effect was opposite. The G allele of the SNP in Chinese population is a protective allele (OR = 0.62, 95 % CI 0.44-0.87), while it was the risk allele for African population (OR = 1.19, 95 % CI 1.12-1.26). No significance was found for SNP rs2335704. The results provided an independent support for a role in susceptibility to TB for SNP rs4331426. However, it also indicated that direct predisposition element to TB and the association effects may vary across ethnic groups.

Bronchoscopy for the diagnosis of pulmonary tuberculosis in patients with negative sputum smear microscopy results

OBJECTIVE

To evaluate the diagnostic accuracy of bronchoscopy in patients with clinical or radiological suspicion of tuberculosis who were unable to produce sputum or with negative sputum smear microscopy results.

METHODS

A prospective cross-sectional study involving 286 patients under clinical or radiological suspicion of having pulmonary tuberculosis and submitted to bronchoscopy-BAL and transbronchial biopsy (TBB). The BAL specimens were submitted to direct testing and culture for AFB and fungi, whereas the TBB specimens were submitted to histopathological examination.

RESULTS

Of the 286 patients studied, 225 (79%) were diagnosed on the basis of bronchoscopic findings, as follows: pulmonary tuberculosis, in 127 (44%); nonspecific chronic inflammation, in 51 (18%); pneumocystis, fungal infections, or nocardiosis, in 20 (7%); bronchiolitis obliterans organizing pneumonia, alveolites, or pneumoconiosis, in 14 (5%); lung or metastatic neoplasms, in 7 (2%); and nontuberculous mycobacterium infections, in 6 (2%). For the diagnosis of tuberculosis, BAL showed a sensitivity and a specificity of 60% and 100%, respectively. Adding the TBB findings significantly increased this sensitivity (to 84%), as did adding the post-bronchoscopy sputum smear microscopy results (total sensitivity, 94%). Minor post-procedure complications occurred in 5.6% of the cases.

CONCLUSIONS

Bronchoscopy is a reliable method for the diagnosis of pulmonary tuberculosis, with low complication rates. The combination of TBB and BAL increases the sensitivity of the method and facilitates the differential diagnosis with other diseases.

Evaluation of in-house PCR for diagnosis of smear-negative pulmonary tuberculosis in Kampala, Uganda

Background

Nucleic acid amplification tests (NAATs) have offered hope for rapid diagnosis of tuberculosis (TB). However, their efficiency with smear-negative samples has not been widely studied in low income settings. Here, we evaluated in-house PCR assay for diagnosis of smear-negative TB using Lowenstein-Jensen (LJ) culture as the baseline test. Two hundred and five pulmonary TB (PTB) suspects with smear-negative sputum samples, admitted on a short stay emergency ward at Mulago Hospital in Kampala, Uganda, were enrolled. Two smear-negative sputum samples were obtained from each PTB suspect and processed simultaneously for identification of MTBC using in-house PCR and LJ culture.

Results

Seventy two PTB suspects (35%, 72/205) were LJ culture positive while 128 (62.4%, 128/205) were PCR-positive. The sensitivity and specificity of in-house PCR for diagnosis of smear-negative PTB were 75% (95% CI 62.6-85.0) and 35.9% (95% CI 27.2-45.3), respectively. The positive and negative predictive values were 39% (95% CI 30.4-48.2) and 72.4% (95% CI 59.1-83.3), respectively, while the positive and negative likelihood ratios were 1.17 (95% CI 0.96-1.42) and 0.70 (95% CI 0.43-1.14), respectively. One hundred and seventeen LJ culture-negative suspects (75 PCR-positive and 42 PCR-negative) were enrolled for follow-up at 2 months. Of the PCR-positive suspects, 45 (60%, 45/75) were still alive, of whom 29 (64.4%, 29/45) returned for the follow-up visit; 15 (20%, 15/75) suspects died while another 15 (20%, 15/75) were lost to follow-up. Of the 42 PCR-negative suspects, 22 (52.4%, 22/42) were still alive, of whom 16 (72.7%, 16/22) returned for follow-up; 11 (26.2%, 11/42) died while nine (21.4%, 9/42) were lost to follow-up. Overall, more PCR-positive suspects were diagnosed with PTB during follow-up visits but the difference was not statistically significant (27.6%, 8/29 vs. 25%, 4/16, p = 0.9239). Furthermore, mortality was higher for the PCR-negative suspects but the difference was also not statistically significant (26.2% vs. 20% p = 0.7094).

Conclusion

In-house PCR correlates poorly with LJ culture for diagnosis of smear-negative PTB. Therefore, in-house PCR may not be adopted as an alternative to LJ culture.

Interferon-gamma release assay performance in pulmonary and extrapulmonary tuberculosis

BACKGROUND

The diagnosis of tuberculosis remains difficult. This study aimed to assess performance of interferon-gamma release assay (IGRA) in diagnosis of active tuberculosis (ATB) with pulmonary and extrapulmonary involvements, and to determine the diagnostic role of IGRA (T-SPOT.TB) and tuberculin skin test (TST) in BCG-vaccinated population.

METHODS AND FINDINGS

Two hundred twenty-six ATB suspects were recruited and examined with T-SPOT.TB. Among them, fifty-two and seventy-six subjects were simultaneously tested by TST with 5TU or 1TU of purified protein derivative (PPD). The sensitivity of T-SPOT.TB was 94.7% (71/75), comparable in pulmonary and extrapulmonary disease groups (95.6% vs. 93.3%, P>0.05), while the specificity was 84.10% (90/107) but differed in two groups (69.2% vs. 88.9%, P = 0.02). Compared to T-SPOT.TB, TST with 5TU-PPD showed less sensitivity (92.3% vs. 56.4%) and specificity (84.6% vs. 61.5%) (both P<0.01); the sensitivity of TST with 1TU-PPD was 27.8%, and despite its specificity identical to T-SPOT.TB (both 82.8%) positive predictive value (PPV) was only 33.3%. By combining T-SPOT.TB with TST (1TU), the specificity rose to 95%, but the PPV stayed unchanged.

CONCLUSIONS

IGRA could function as a powerful immunodiagnostic test to explore pulmonary and extrapulmonary TB, while TST failed to play a reliable or auxiliary role in identifying TB disease and infection in the BCG-vaccinated population.

Longitudinal analysis of QuantiFERON-TB Gold In-Tube in children with adult household tuberculosis contact in South Africa: a prospective cohort study

BACKGROUND

QuantiFERON-TB Gold In Tube (QFT-GIT) is a tool for detecting M. tuberculosis infection. However, interpretation and utility of serial QFT-GIT testing of pediatric tuberculosis (TB) contacts is not well understood. We compared TB prevalence between baseline and 6 months follow-up using QFT-GIT and tuberculin skin testing (TST) in children who were household contacts of adults with pulmonary TB in South Africa, and explored factors associated with QFT-GIT conversions and reversions.

METHOD

Prospective study with six month longitudinal follow-up.

RESULTS

Among 270 enrolled pediatric contacts, 196 (73%) underwent 6-month follow-up testing. The 6-month prevalence estimate of MTB infection in pediatric contacts increased significantly from a baseline of 29% (79/270, 95%CI [24-35]) to 38% (103/270, 95% CI [32-44], p<0.001) using QFT-GIT; prevalence increased from a baseline of 28% (71/254, 95%CI [23-34]) to 33% (88/263, 95%CI [21-32], p = 0.002) using TST. Prevalence estimates were influenced by thresholds for positivity for TST, but not for QFT-GIT. Among 134 children with a negative or indeterminate baseline QFT-GIT, 24 (18%) converted to positive at follow-up; conversion rates did not differ significantly when using more stringent thresholds to define QFT-GIT conversion. Older age >10 years (AOR 8.9 95%CI [1.1-72]) and baseline TST positivity ≥5 mm (AOR 5.2 95%CI [1.2-23]) were associated with QFT-GIT conversion. Among 62 children with a positive baseline QFT-GIT, 9 (15%) reverted to negative; female gender (AOR 18.5 95%CI [1.1-321]; p = 0.04] was associated with reversion, while children with baseline positive TST were less likely to have QFT-GIT reversion (AOR 0.01 95%CI [0.001-0.24]).

CONCLUSION

Among pediatric contacts of adult household TB cases in South Africa, prevalence estimates of TB infection increased significantly from baseline to 6 months. Conversions and reversions occurred among pediatric TB contacts using QFT-GIT, but QFT-GIT conversion rates were less influenced by thresholds used for conversions than were TST conversion rates.

Whole-blood interferon-gamma release assay for diagnosis of tuberculous lymphadenitis

Tuberculosis remains a major problem for much of the world. Tuberculous lymphadenitis is the most common type of extrapulmonary tuberculosis, although a difficult invasive procedure is required for its diagnosis. We evaluated the usefulness of the whole-blood interferon-gamma release assay (IGRA) for diagnosis of tuberculous lymphadenitis. From January 2008 to October 2010, 108 patients underwent lymph node biopsy and the IGRA concurrently in Wonju Christian Hospital, Yonsei University Wonju College of Medicine. Among the patients, 27 were diagnosed with tuberculous lymphadenitis and 81 were diagnosed with non-tuberculous lymphadenitis. The diagnostic performances of the IGRA were evaluated. The median patient age was 33 years (interquartile range [IQR] 23.5 to 48 years), and 28 (25.9%) patients were male. No patient was administered immunosuppressive agents such as high-dose steroids or underwent chemotherapy within 90 days before the IGRA test. The IGRA was positive in 25 of 27 patients with tuberculous lymphadenitis and in 13 of 81 patients with non-tuberculous lymphadenopathy. Therefore, the sensitivity of IGRA was 92.6% (95% CI, 82.0 to 100), and the specificity was 80.2% (95% CI, 71.4 to 89.1). In the patients with positive IGRA results, the INF-γ concentration was significantly higher in the patients with tuberculous lymphadenitis compared to that in the patients without tuberculous lymphadenitis (15.58 [IQR 6.87 to 45.10] IU/mL versus 0.97 [IQR 0.65 to 2.41] IU/mL, p < 0.001). In conclusion, the IGRA is helpful for the diagnosis of tuberculous lymphadenitis.

Comparison of two laboratory-developed PCR methods for the diagnosis of pulmonary tuberculosis in Brazilian patients with and without HIV infection

BACKGROUND

Direct smear examination with Ziehl-Neelsen (ZN) staining for the diagnosis of pulmonary tuberculosis (PTB) is cheap and easy to use, but its low sensitivity is a major drawback, particularly in HIV seropositive patients. As such, new tools for laboratory diagnosis are urgently needed to improve the case detection rate, especially in regions with a high prevalence of TB and HIV.

OBJECTIVE

To evaluate the performance of two in house PCR (Polymerase Chain Reaction): PCR dot-blot methodology (PCR dot-blot) and PCR agarose gel electrophoresis (PCR-AG) for the diagnosis of Pulmonary Tuberculosis (PTB) in HIV seropositive and HIV seronegative patients.

METHODS

A prospective study was conducted (from May 2003 to May 2004) in a TB/HIV reference hospital. Sputum specimens from 277 PTB suspects were tested by Acid Fast Bacilli (AFB) smear, Culture and in house PCR assays (PCR dot-blot and PCR-AG) and their performances evaluated. Positive cultures combined with the definition of clinical pulmonary TB were employed as the gold standard.

RESULTS

The overall prevalence of PTB was 46% (128/277); in HIV+, prevalence was 54.0% (40/74). The sensitivity and specificity of PCR dot-blot were 74% (CI 95%; 66.1%-81.2%) and 85% (CI 95%; 78.8%-90.3%); and of PCR-AG were 43% (CI 95%; 34.5%-51.6%) and 76% (CI 95%; 69.2%-82.8%), respectively. For HIV seropositive and HIV seronegative samples, sensitivities of PCR dot-blot (72% vs 75%; p=0.46) and PCR-AG (42% vs 43%; p=0.54) were similar. Among HIV seronegative patients and PTB suspects, ROC analysis presented the following values for the AFB smear (0.837), Culture (0.926), PCR dot-blot (0.801) and PCR-AG (0.599). In HIV seropositive patients, these area values were (0.713), (0.900), (0.789) and (0.595), respectively.

CONCLUSION

Results of this study demonstrate that the in house PCR dot blot may be an improvement for ruling out PTB diagnosis in PTB suspects assisted at hospitals with a high prevalence of TB/HIV.