Diagnosis of abdominal tuberculosis by T-cell-based assays on peripheral blood and peritoneal fluid mononuclear cells

Meta-analysis of diagnostic accuracy of nucleic acid amplification tests for abdominal tuberculosis

BACKGROUND

Abdominal tuberculosis (TB) is a severe extrapulmonary TB, which can lead to serious complications. Early diagnosis and treatment are very important for the prognosis and the diagnosis of abdominal TB is still difficult.

METHODS

We searched PubMed, the Cochrane Library, Embase, China National Knowledge Infrastructure, and the Wanfang database for studies evaluating the diagnostic accuracy of NAATs for abdominal TB until August 2020. Any types of study design with full text were sought and included. The risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool. Subgroup analysis, meta-regression analysis and sensitivity analysis were used to explore the sources of heterogeneity. Stata version 15.0 with the midas command packages was used to carry out meta-analyses.

RESULTS

We included a total of 78 independent studies from 53 articles; 64 with CRS as the reference standard, and 14 with culture as the reference standard. The pooled sensitivity, specificity, and the areas under summary receiver operating characteristic (SROC) curves (AUC) were 58% (51%-64%; I2 = 87%), 99% (97%-99%; I2 = 81%), and 0.92 (0.89-0.94) compared with CRS, respectively. The pooled sensitivity, specificity, and the AUC values of the SROC were 80% (66%-90%; I2 = 56%), 96% (92%-98%; I2 = 84%), and 0.97 (0.95-0.98) compared with culture, respectively. The heterogeneity of sensitivity and specificity was significant.

CONCLUSIONS

NAATs had excellent efficacy in the diagnosis of abdominal TB regardless of the reference standard and regardless of the subtype of abdominal TB. Multiplex PCR with multiple target genes may improve diagnostic sensitivity, and stool specimens may also be used for the diagnosis of abdominal TB in addition to tissue and ascites.

Value of gamma interferon enzyme-linked immunospot assay in the diagnosis of peritoneal dialysis-associated tuberculous peritonitis

Background

Tuberculous peritonitis is the most common form of extrapulmonary tuberculosis infection in peritoneal dialysis patients. However, diagnosing tuberculous peritonitis quickly and early has always been a challenge for nephrologists. Mycobacterium tuberculosis antigen-specific gamma interferon enzyme-linked immunospot (IFN-γ ELISPOT) assay has been widely used in the clinical diagnosis of tuberculous pleurisy and peritonitis, but its use has not been reported for uremia.

Methods

This study mainly verified the feasibility of using the M. tuberculosis antigen-specific IFN-γ ELISPOT assay in the diagnosis of continuous ambulatory peritoneal dialysis (CAPD) patients with tuberculous peritonitis. Taking M. tuberculosis culture as the gold standard, the IFN-γ ELISPOT assay was used to analyze peripheral blood and peritoneal dialysis fluid of patients, and the receiver operating characteristic (ROC) curves in patients with tuberculous peritonitis (TBP) or non-tuberculous peritonitis (NTBP) were analyzed.

Results

The area under the receiver operating characteristic curve (AUC) was 0.927 (95% CI 0.816–1.000, P = 0.001) for the ELISPOT assay with peritoneal fluid mononuclear cells (PFMC), which was higher than that for the ELISPOT assay with peripheral blood mononuclear cells (PBMC) (0.825, 95% CI 0.6490–1.000, P = 0.011). The cutoff value for the diagnosis of TBP was 40 spot-forming cells (SFCs)/2 × 10⁵ for the ELISPOT with PBMC, with a sensitivity of 55.6%, a specificity of 92.3%, and a diagnostic efficiency of 77.3%. The cutoff value for the diagnosis of TBP was 100 SFCs/2 × 10⁵ for the ELISPOT on PFMC, with a sensitivity, specificity, and diagnostic efficiency 77.8%, 84.6%, and 81.8%, respectively. Parallel and serial testing algorithms appeared more accurate than single ELISPOT assays with PBMC, but ELISPOT assays with PFMC.

Conclusions

The IFN-γ release test can be used for the early diagnosis of CAPD-related TBP; compared with peripheral blood, peritoneal fluid may be a more effective and accurate medium to diagnose CAPD complicated with tuberculous peritonitis.

Diagnostic Value of T-SPOT.TB Assay for Tuberculous Peritonitis: A Meta-Analysis

Background: Tuberculous peritonitis (TP) is a common form of abdominal tuberculosis (TB). Diagnosing TP remains challenging in clinical practice. The aim of the present meta-analysis was to evaluate the diagnostic accuracy of peripheral blood (PB) T-SPOT and peritoneal fluid (PF) T-SPOT for diagnosing TP.

Methods: PubMed, EmBase, Cochrane, Scopus, Google scholar, China national knowledge internet, and Wan-Fang databases were searched for relevant articles from August 1, 2005 to July 5, 2020. Statistical analysis was performed using Stata, Revman, and Meta-Disc software. Diagnostic parameters including pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were determined. Summary receiver operating characteristic curve was used to determine the area under the curve (AUC).

Results: Twelve studies were eligible and included in the meta-analysis. The analysis showed that the pooled sensitivity and specificity of PB T-SPOT in diagnosing TP were 0.91 (95% CI, 0.88–0.94) and 0.78 (95% CI, 0.73–0.81), respectively, while the pooled PLR, NLR, and DOR were 4.05 (95% CI, 2.73–6.01), 0.13 (95% CI, 0.07–0.23), and 37.8 (95% CI, 15.04–94.98), respectively. On the other hand, the summary estimates of sensitivity, specificity, PLR, NLR, and DOR of PF T-SPOT for TP diagnosis were 0.90 (95% CI, 0.85–0.94), 0.78 (95% CI, 0.72–0.83), 6.35 (95% CI, 2.67–15.07), 0.14 (95% CI, 0.09–0.21), and 58.22 (95% CI, 28.76–117.83), respectively. Furthermore, the AUC of PB T-SPOT and PF T-SPOT for TP diagnosis were 0.91 and 0.94, respectively.

Conclusions: Our results indicate that both PB T-SPOT and PF T-SPOT can be served as sensitive approaches for the diagnosis of TP. However, the unsatisfactory specificities of these two methods limit their application as rule-in tests for TP diagnosis. Furthermore, the standardization of the operating procedure of PF T-SPOT is further needed.

Utility of T-cell interferon-γ release assays for the diagnosis of female genital tuberculosis in a tertiary referral hospital in Beijing, China

Diagnosis of female genital tuberculosis (FGTB) remains a challenge. The aim of this study was to evaluate the diagnostic value of T-SPOT.TB on peripheral blood mononuclear cells (PBMCs) for diagnosing FGTB in an area with high TB burden.Patients with suspected FGTB were enrolled consecutively between August 2010 and August 2015. T-SPOT.TB on PBMCs and histopathology were performed in all patients. T-SPOT.TB results were evaluated against patients' final diagnosis of FGTB which was made based on clinical manifestations, radiology, microbiological and histopathological evaluation, and response to anti-TB treatment. The sensitivity, specificity, predictive value, and likelihood ratio of T-SPOT.TB were analyzed.Among the 66 patients enrolled, 32 were diagnosed with confirmed FGTB, 33 with non-TB including ovarian tumor in 10 patients (30%), pelvic inflammatory diseases in 8 patients (24%), endometriosis in 7 patients (21%), endometrial polyps in 3 patients (9%), abscess of fallopian tube in 2 patients (6%), cyst of fallopian tube in 2 patients (6%), and endometrial carcinoma in 1 patient (3%). One patient with clinically indeterminate diagnosis was not included in the final analysis. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio, and negative likelihood ratio of T-SPOT.TB on PBMCs for diagnosis of FGTB were 94%, 70%, 75%, 92%, 3.09, and 0.09, respectively. Frequencies of spot forming cells (SFCs) of T-SPOT.TB were 430 (interquartile range [IQR] 155-706) SFCs/10 PBMCs and 124 (IQR 61-313) SFCs/10 PBMCs in FGTB and non-TB patients, respectively, and the difference was statistically significant (P = 2.14 × 10). By receiver operating characteristic curve analysis, a cutoff value of 40 SFCs/10 PBMCs of T-SPOT.TB had a sensitivity of 94% and specificity of 76% for the diagnosis of FGTB.T-SPOT.TB on PBMCs appeared to be a valuable and rapid diagnostic method for FGTB in TB endemic settings with high sensitivity and NPV.

Guidelines for the use of interferon-γ release assays in the diagnosis of tuberculosis infection

INTRODUCTION

Interferon-gamma release assays are widely used for the diagnosis of tuberculosis infection in low-prevalence countries. However, there is no consensus on their application. The objective of this study was to develop guidelines for the use of interferon-gamma release assays in specific clinical scenarios in Spain.

METHODS

A panel of experts comprising specialists in infectious diseases, respiratory diseases, microbiology, pediatrics and preventive medicine, together with a methodologist, formulated the clinical questions and outcomes of interest. They conducted a systematic literature search, summarized the evidence and rated its quality, and prepared the recommendations following the GRADE (Grading of Recommendations of Assessment Development and Evaluations) methodology.

RESULTS

The panel prepared recommendations on the use of interferon-gamma release assays for the diagnosis of tuberculosis infection in the contact-tracing study (both adults and children), health care workers, immunosuppressed patients (patients infected with human immunodeficiency virus, patients with chronic immunomediated inflammatory diseases due to start biological therapy and patients requiring organ transplant) and for the diagnosis of active tuberculosis. Most recommendations were weak, mainly due to the lack of good quality evidence to balance the clinical benefits and disadvantages of the interferon-gamma release assays as compared with the tuberculin skin test.

CONCLUSION

This document provides evidence-based guidance on the use of interferon-gamma release assays for the diagnosis of tuberculosis infection in patients at risk of tuberculosis or with suspicion of active disease. The guidelines will be applicable in specialist and primary care and in public health settings.

Leukemias involving abdominal and pelvic lymph nodes: evaluation with contrast-enhanced MDCT

PURPOSE

To clarify features of lymph nodes associated with leukemia purposing to offer help for imaging diagnosis and differential diagnosis of leukemia.

MATERIALS AND METHODS

We retrospectively analyzed 47 patients with clinically proven leukemia involving the abdominal and pelvic lymph nodes. Of these 47 patients, 10 had acute myeloid leukemia, 9 had acute lymphocytic leukemia, and 28 had chronic lymphocytic leukemia. MDCT was used to determine lymph node features such as morphology, growth patterns, size, enhancement patterns, anatomical distribution, and manifestations in extramedullary organs.

RESULTS

Incidence of leukemia was higher in men than in women. Enlarged lymph nodes were more frequently conglomerated in chronic lymphocytic leukemia (96.4%) than in acute myeloid leukemia (50%) and acute lymphocytic leukemia (55.6%; P < 0.05 for both). Lymph nodes associated with chronic lymphocytic leukemia were larger than those associated with acute myeloid and lymphocytic leukemias (P < 0.05 for both). The enlarged lymph nodes appeared homogeneous (80.9%) and homogeneous mixed with peripheral (19.1%). No statistically significant differences were observed between the three types of leukemias with respect to enhancement patterns (all P > 0.05). The lymph nodes commonly associated with these three leukemias were located in the lesser omentum, upper and lower para-aortic regions, and groin region.

CONCLUSIONS

Our study showed that contrast-enhanced MDCT could accurately determine the enhancement patterns and anatomical distribution of lymph nodes associated with leukemia. Therefore, it is helpful for imaging diagnosis and differential diagnosis of leukemia.

Peripancreatic tuberculous lymphadenopathy masquerading as pancreatic malignancy: a single-center experience

BACKGROUND AND AIM

Peripancreatic tuberculous lymphadenopathy is very rare and can be misdiagnosed with pancreatic or peripancreatic malignancies. The clinical characteristics and treatment outcome have not been well known. Herein, we investigated the accuracy of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA), clinical features, and treatment outcomes.

METHODS

We retrospectively analyzed 42 patients diagnosed with peripancreatic tuberculosis between December 2004 and January 2011 at the tertiary care hospital in Korea.

RESULTS

Median age was 36 years (interquartile range, 30-55), and female was 66.7% (28/42). Nineteen patients (45.2%) had no symptoms, while the others had non-specific various symptoms. Thirteen (31.0%) had a previous history of tuberculosis. Initial impressions of the mass were pancreatic cancer in 14 (33.3%) and tuberculous lymphadenopathy in 13 patients (31.0%). EUS-FNA was performed in all 42 patients, with a diagnostic yield of pathologic examinations in 80.5%, polymerase chain reaction for tuberculosis in 42.9%, culture in 47.4%, and acid-fast bacilli staining in 10.0%. Tuberculosis is confirmed in 28 (66.7%), and probable tuberculosis in 14 (33.3%). All patients received anti-tuberculosis treatment, a 6-months regimen in 12 (28.6%) and a 9-months regimen in 28 (66.7%). Treatment response evaluated in 35 patients (83.3%) by computed tomography criteria showed complete response in 10 patients (28.6%), partial response in 23 (65.7%), stable disease in 1 (2.9%), and progressive disease in 1 (2.9%).

CONCLUSIONS

Peripancreatic tuberculous lymphadenopathy is frequently mistaken for pancreatic malignancy. EUS-FNA can be helpful for an accurate diagnosis. Complete resolution of the lesion, however, was not common on following imaging study after treatment.

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.

Indeterminate T-SPOT.TB Test Results in Patients with Suspected Extrapulmonary Tuberculosis in Routine Clinical Practice

Background

The two interferon-γ release assays such as QuantiFERON-TB Gold / In-Tube (QFT-TB) and T-SPOT.TB-are useful tools for the rapid diagnosis of tuberculosis (TB) but can yield indeterminate test results (ITRs). While some studies have identified risk factors for ITRs in the QFT-TB test, there have been few such studies for the T-SPOT.TB test. The aim of this study was to investigate the risk factors associated with ITRs in the T-SPOT.TB test.

Materials and Methods

From April 2008 to August 2010, all patients with suspected extrapulmonary tuberculosis (E-TB) were enrolled in a tertiary hospital in Korea. ITR was defined as < 20 spots in the positive control well or > 10 spots in the negative control well.

Results

Out of a total of 368 patients, 32 (8.7%, 95% CI, 6.0% to 11.7%) had ITRs in their T-SPOT.TB tests. The ITRs were due to a low mitogen response in 13 (40.6%) patients and to a high nil response in the other 19 (59.4%) patients. Statistical analysis revealed that old age, underlying diseases, immunosuppressive treatment, lymphopenia, and clinical manifestations of E-TB were not significantly associated with ITRs.

Conclusions

Indeterminate results in the T-SPOT.TB test are not affected by age, underlying disease, immunosuppressive treatment, lymphopenia, or clinical manifestations of E-TB, which are known risk factors for indeterminate results in the QFT-TB test.

Assessment by meta-analysis of interferon-gamma for the diagnosis of tuberculous peritonitis

AIM: To investigate the performance and diagnostic accuracy of interferon-gamma (IFN-γ) for tuberculous peritonitis (TBP) by meta-analysis.

METHODS: A systematic search of English language studies was performed. We searched the following electronic databases: MEDLINE, EMBASE, Web of Science, BIOSIS, LILACS and the Cochrane Library. The Standards for Reporting Diagnostic Accuracy initiative and Quality Assessment for Studies of Diagnostic Accuracy tool were used to assess the methodological quality of the studies. Sensitivity, specificity, and other measures of the accuracy of IFN-γ concentration in the diagnosis of peritoneal effusion were pooled using random-effects models. Receiver operating characteristic (ROC) curves were applied to summarize overall test performance. Two reviewers independently judged study eligibility while screening the citations.

RESULTS: Six studies met the inclusion criteria. The average inter-rater agreement between the two reviewers for items in the quality checklist was 0.92. Analysis of IFN-γ level for TBP diagnosis yielded a summary estimate: sensitivity, 0.93 (95%CI, 0.87-0.97); specificity, 0.99 (95%CI, 0.97-1.00); positive likelihood ratio (PLR), 41.49 (95%CI, 18.80-91.55); negative likelihood ratio (NLR), 0.11 (95%CI, 0.06-0.19); and diagnostic odds ratio (DOR), 678.02 (95%CI, 209.91-2190.09). χ² values of the sensitivity, specificity, PLR, NLR and DOR were 5.66 (P = 0.3407), 6.37 (P = 0.2715), 1.38 (P = 0.9265), 5.46 (P = 0.3621) and 1.42 (P = 0.9220), respectively. The summary receiver ROC curve was positioned near the desirable upper left corner and the maximum joint sensitivity and specificity was 0.97. The area under the curve was 0.99. The evaluation of publication bias was not significant (P = 0.922).

CONCLUSION: IFN-γ may be a sensitive and specific marker for the accurate diagnosis of TBP. The level of IFN-γ may contribute to the accurate differentiation of tuberculosis (TB) ascites from non-TB ascites.

Solitary pancreatic tuberculosis: A case report and literature review

AIM: To analyze the clinical characteristics of and diagnostic methods for solitary pancreatic tuberculosis.

METHODS: A case of solitary pancreatic tuberculosis was reported. In addition, 48 similar cases in published Chinese literature were identified to conduct a literature review. The data were identified by searching CNKI and CBM databases and browsing the relevant reference lists. The keywords were "pancreatic tuberculosis" and "tuberculosis and pancreas". The clinical manifestations were analyzed by descriptive methods. Criteria for the diagnosis of solitary pancreatic tuberculosis were: all lesions localized only in the pancreas and neighboring tissues, no other detectable foci of tuberculosis, no history of tuberculosis, having a clear chest radiograph, and a positive histological diagnosis.

RESULTS: Predominant symptoms consisted of abdominal pain (63.27%), weight loss (59.18%), fever (36.73%), jaundice (34.69%), and abdominal distention/bloating, without night sweats. Most patients were misdiagnosed with pancreatic tumors, and other misdiagnoses were pseudo-pancreatic cysts, chronic cholecystitis with pancreatitis, and cholecystic tumors. Erythrocyte sedimentation rate was elevated in 85.71% (12/14) of cases; PPD test was strongly positive in 55.56% (5/9); and CA19-9 was mildly elevated in 25% (2/8). CT scans showed a pancreatic mass (31/41) with heterogeneous hypodensity focus (9/41), calcification (6/41), or peripancreatic nodal enlargement (14/41). Ultrasound or CT-guided biopsies were performed in 8.16% (4/49) of cases, including one undergoing EUS-guided fine needle aspiration for cytologic diagnosis. Laparotomy was performed in 45 of 49 cases, and most received combined antituberculosis therapy. Anti-tuberculosis therapy was successful in 42 of 49 cases.

CONCLUSION: Solitary pancreatic tuberculosis is a rare condition with no specific clinical manifestations. The possibility of solitary pancreatic tuberculosis should be considered in patients presenting with a pancreatic mass and irregular pancreas enlargement. Diagnosis should be made cytologically, and laparotomy can be avoided if a definitive diagnosis was established before surgery. Solitary pancreatic tuberculosis can be effectively cured by antituberculosis therapy.

Predictive value of interferon-γ ELISPOT assay in HIV 1-infected patients in an intermediate tuberculosis-endemic area

The tuberculin skin test for diagnosing latent tuberculosis (TB) has some limitations for HIV-infected patients, especially in BCG vaccinated countries. The objective of this study was to identify the incidence rate of new TB cases among HIV-infected patients in an intermediate TB-endemic area and to examine its correlation with the ELISPOT assay. We prospectively followed up 124 patients with HIV-1 infection to monitor development of active TB disease after performing an ELISPOT assay (T-SPOT. TB test, Oxford Immunotec, Ltd., Abingdon, UK). A total of 120 patients were followed for a median of 947 days; four patients with active TB at enrollment were excluded. Eleven patients developed active TB during 238 person-years, giving a high incidence rate of 4621/100,000 person-years. Patients with positive ELISPOT responses had a higher TB incidence rate than those with negative ELISPOT responses; however this was not statistically significant [20% (6/30) vs. 6.02% (5/83), p=0.052]. A Cox regression analysis showed that the independent risk factors associated with progression of TB were low CD4(+) T cell counts, previous history of TB treatment, and positive ELISPOT results. Advanced HIV-infected patients who showed a positive TB ELISPOT assay had a higher rate of progression to TB in the intermediate TB-endemic area.

Interferon-gamma release assays for the diagnosis of extrapulmonary tuberculosis: a systematic review and meta-analysis

Interferon -gamma release assays (IGRAs) provide a new diagnostic method for Mycobacterium tuberculosis (TB) infection. However, the diagnostic value of IGRAs for extrapulmonary TB (EPTB) has not been clarified. We searched several databases and selected papers with strict inclusion criteria, evaluated the evidence of commercially available IGRAs (QuantiFERON(®) -TB Gold QFT-G or QFT-GIT and T-SPOT(®) .TB) on blood and the tuberculin skin test (TST) using random effects models. Twenty studies with 1711 patients were included. After excluding indeterminate results, pooled sensitivity for the diagnosis of EPTB was 72% [95% confidence interval (CI) 65-79%] for QFT-G or GIT and 90% (95% CI, 86-93%) for T-SPOT; in high-income countries the sensitivity of QFT-G or GIT (79%, 95% CI 72-86%) was much higher than that (29%, 95% CI 14-48%) in low/middle-income countries. Pooled specificity for EPTB was 82% (95% CI 78-87%) for QFT-G or GIT and 68% (95% CI 64-73%) for T-SPOT. Pooled sensitivity of TST from four studies in high-income countries was lower than that of IGRAs. T-SPOT was more sensitive in detecting EPTB than QFT-G or GIT and TST. However, both IGRAs and TST have similar specificity for EPTB. IGRAs have limited value as diagnostic tools to screen and rule out EPTB, especially in low/middle-income countries. The immune status of patients does not affect the diagnostic accuracy of IGRAs for EPTB.

Adjunctive tests for diagnosis of tuberculosis: serology, ELISPOT for site-specific lymphocytes, urinary lipoarabinomannan, string test, and fine needle aspiration

The diagnostic gold standard for active tuberculosis (TB) is the detection of Mycobacterium tuberculosis (MTB) by culture or molecular methods. However, despite its limited sensitivity, sputum smear microscopy is still the mainstay of TB diagnosis in resource-limited settings. Consequently, diagnosis of smear-negative pulmonary and extrapulmonary TB remains challenging in such settings. A number of novel or alternative techniques could provide adjunctive diagnostic use in the context of difficult-to-diagnose TB. These may be especially useful in certain patient groups such as persons infected with human immunodeficiency virus (HIV) and children, who are disproportionably affected by smear-negative and extrapulmonary disease and who are also most adversely affected by delays in TB diagnosis and treatment. We review a selection of these methods that are independent of nucleic acid amplification techniques and could largely be implemented in resource-limited settings in current or adapted versions. Specifically, we discuss the diagnostic use and potential of serologic tests based on detection of antibodies to MTB antigens; interferon gamma release assays using site-specific lymphocytes; detection of lipoarabinomannan, a glycolipid of MTB, in urine; the string test, a novel technique to retrieve lower respiratory tract samples; and fine needle aspiration biopsy of lymph nodes.

T-SPOT.TB assay usage in adults and children

The diagnosis and treatment of TB infection is one of the public health priorities. Until recently, diagnosis of TB infection has been based on the tuberculin skin test (TST). However, this is neither 100% sensitive nor specific for the diagnosis of TB infection owing to its many drawbacks. More recently, T-cell-based IFN-γ release assays (IGRAs) have been developed. In this article, we review the clinical performance of one of the IGRAs, T-SPOT.TB assay, for the diagnosis of TB infection in adults and children. We discuss the principle of the assay, its utility in active TB diseases, latent TB infection and the performance of the test in specialized subgroups of patients, such as immunocompromised individuals. When compared with the TST, the T-SPOT.TB assay has better specificity in bacillus Calmette-Guérin-vaccinated individuals, and data suggest that T-SPOT.TB may be more sensitive than the TST. Data in groups at high risk of progression to disease support the idea that T-SPOT.TB performs better than the TST. In addition, application of T-SPOT.TB by using bodily fluids such as cerebrospinal fluid, bronchoalveolar lavage fluid and pleural fluid may offer new diagnostic approaches in extrapulmonary TB disease. Although IGRAs cannot distinguish active TB disease from latent TB infection, these assays perform better than the TST for the detection of TB infection.

A prospective longitudinal study evaluating the usefulness of a T-cell-based assay for latent tuberculosis infection in kidney transplant recipients

We evaluated whether ELISPOT assay can predict tuberculosis (TB) development in kidney-transplantation (KT) recipients with a negative tuberculin skin test (TST). All adult patients admitted to a KT institute between June 2008 and December 2009 were enrolled; TB development after KT was observed between June 2008 and December 2010. Isoniazid (INH) was given to those patients with positive TST or clinical risk factors for latent TB infection (LTBI). ELISPOT assay was performed on all patients, and TB development after KT was observed by a researcher blinded to the results of ELISPOT. A total of 312 KT recipients including 242 (78%) living-donor KT were enrolled. Of the 312 patients, 40 (13%) had positive TST or clinical risk factors for LTBI and received INH; none developed TB after KT. Of the remaining 272 patients, 4 (6%) of 71 with positive ELISPOT assay developed TB after KT, whereas none of the 201 patients with negative (n = 171) or indeterminate ELISPOTs (n = 30) developed TB after KT (rate difference between positive and negative/indeterminate ELISPOT, 3.3 per 100 person-years [95% CI 1.4-5.1, p<0.001]). Positive ELISPOT results predict subsequent development of TB in KT recipients in whom LTBI cannot be detected by TST or who lack clinical risk factors for LTBI.

Diagnostic performance of T-SPOT.TB for extrapulmonary tuberculosis according to the site of infection

BACKGROUND

The clinical manifestations of extrapulmonary tuberculosis (E-TB) vary according to site of disease, so we tested the hypothesis that IFN-γ producing T-cell responses also vary in parallel. Therefore we conducted a prospective, blinded, observational study to evaluate the diagnostic performance of blood T-SPOT.TB according to the various sites of E-TB.

METHODS

From April 2008 to August 2010, all patients with suspected E-TB were enrolled at a tertiary hospital in an intermediate TB-burden country. Final diagnosis in patients with suspected E-TB was classified by clinical category.

RESULTS

A total of 368 patients with suspected E-TB were enrolled; 196 (53%) were classified as having TB, including 119 (32%) with confirmed TB, 34 (9%) probable TB, and 43 (12%) possible TB; the remaining 172 (47%) were classified as not having TB. After excluding patients with possible TB, the T-SPOT.TB was more sensitive in patients with chronic forms of E-TB such as lymph node or osteoarticular TB (93%, 95% CI 83%-97%) than in patients with acute forms of E-TB such as TB meningitis or miliary TB (79%, 95% CI 66%-87%, P = 0.03).

CONCLUSIONS

The diagnostic performance of the blood T-SPOT.TB differs among patients with various clinical manifestations of E-TB.

The immunology of tuberculosis: from bench to bedside

Tuberculosis (TB) is an international public health priority and kills almost two million people annually. TB is out of control in Africa due to increasing poverty and HIV coinfection, and drug-resistant TB threatens to destabilize TB control efforts in several regions of the world. Existing diagnostic tools and therapeutic interventions for TB are suboptimal. Thus, new vaccines, immunotherapeutic interventions and diagnostic tools are urgently required to facilitate TB control efforts. An improved understanding of the immunopathogenesis of TB can facilitate the identification of correlates of immune protection, the design of effective vaccines, the rational selection of immunotherapeutic agents, the evaluation of new drug candidates, and drive the development of new immunodiagnostic tools. Here we review the immunology of TB with a focus on aspects that are clinically and therapeutically relevant. An immunologically orientated approach to tackling TB can only succeed with concurrent efforts to alleviate poverty and reduce the global burden of HIV.

Immunologic paradox in the diagnosis of tuberculous meningitis

We report a patient with microbiologically documented tuberculous meningitis showing that the therapeutic paradox, a therapy-induced switch to a neutrophil-predominant situation in the differential cell counts of cerebrospinal fluid specimens, had a correlation with an immunologic paradox, an increased Mycobacterium tuberculosis-specific gamma interferon-producing T-cell response.