Questionable role of interferon-γ assays for smear-negative pulmonary TB in immunocompromised patients

Evaluation of the IP-10 mRNA release assay for diagnosis of TB in HIV-infected individuals

HIV-infected individuals are susceptible to Mycobacterium tuberculosis (M.tb) infection and are at high risk of developing active tuberculosis (TB). Interferon-gamma release assays (IGRAs) are auxiliary tools in the diagnosis of TB. However, the performance of IGRAs in HIV-infected individuals is suboptimal, which limits clinical application. Interferon-inducible protein 10 (IP-10) is an alternative biomarker for identifying M.tb infection due to its high expression after stimulation with M.tb antigens. However, whether IP-10 mRNA constitutes a target for the diagnosis of TB in HIV-infected individuals is unknown. Thus, we prospectively enrolled HIV-infected patients with suspected active TB from five hospitals between May 2021 and May 2022, and performed the IGRA test (QFT-GIT) alongside the IP-10 mRNA release assay on peripheral blood. Of the 216 participants, 152 TB patients and 48 non-TB patients with a conclusive diagnosis were included in the final analysis. The number of indeterminate results of IP-10 mRNA release assay (13/200, 6.5%) was significantly lower than that of the QFT-GIT test (42/200, 21.0%) (P = 0.000026). IP-10 mRNA release assay had a sensitivity of 65.3% (95%CI 55.9% - 73.8%) and a specificity of 74.2% (95%CI 55.4% - 88.1%), respectively; while the QFT-GIT test had a sensitivity of 43.2% (95%CI 34.1% - 52.7%) and a specificity of 87.1% (95%CI 70.2% - 96.4%), respectively. The sensitivity of the IP-10 mRNA release assay was significantly higher than that of QFT-GIT test (P = 0.00062), while no significant difference was detected between the specificities of these two tests (P = 0.198). The IP-10 mRNA release assay showed a lower dependence on CD4⁺ T cells than that of QFT-GIT test. This was evidenced by the fact that the QFT-GIT test had a higher number of indeterminate results and a lower sensitivity when the CD4⁺ T cells counts were decreased (P < 0.05), while no significant difference in the number of indeterminate results and sensitivity were observed for the IP-10 mRNA release assay among HIV-infected individuals with varied CD4⁺T cells counts (P > 0.05). Therefore, our study suggested that M.tb specific IP-10 mRNA is a better biomarker for diagnosis of TB in HIV-infected individuals.

Review and Updates on the Diagnosis of Tuberculosis

Diagnosis of tuberculosis, and especially the diagnosis of extrapulmonary tuberculosis, still faces challenges in clinical practice. There are several reasons for this. Methods based on the detection of Mycobacterium tuberculosis (Mtb) are insufficiently sensitive, methods based on the detection of Mtb-specific immune responses cannot always differentiate active disease from latent infection, and some of the serological markers of infection with Mtb are insufficiently specific to differentiate tuberculosis from other inflammatory diseases. New tools based on technologies such as flow cytometry, mass spectrometry, high-throughput sequencing, and artificial intelligence have the potential to solve this dilemma. The aim of this review was to provide an updated overview of current efforts to optimize classical diagnostic methods, as well as new molecular and other methodologies, for accurate diagnosis of patients with Mtb infection.

Diagnostic accuracy of interferon-gamma release assays for diagnosis of smear-negative pulmonary tuberculosis: a systematic review and meta-analysis

Introduction

The diagnosis of smear-negative pulmonary tuberculosis (SNPTB) is challenging. Interferon gamma-release assays (IGRAs) may be helpful in early diagnosis among these patients resulting in prompt treatment and favorable outcomes.

Methods

We performed a comprehensive search from each databases’ inception to April 5, 2021. The studies that provided sufficient data regarding the sensitivity and specificity of IGRAs included QuantiFERON-TB Gold In-Tube (QFT-GIT), T-SPOT.TB, or QuantiFERON-TB Gold Plus for diagnosis of SNPTB were included.

Results

Of 1,312 studies screened, 16 studies were included; 11 QFT-GIT, 2 T-SPOT.TB, and 3 QFT-GIT and T-SPOT.TB. For diagnosis of SNPTB, QFT-GIT had sensitivity of 0.77 (95% CI 0.71–0.82), specificity of 0.70 (95% CI 0.58–0.80), diagnostic odds ratio (DOR) of 8.03 (95% CI 4.51–14.31), positive likelihood ratio (LR) of 2.61 (95% CI 1.80–3.80), negative LR of 0.33 (95% CI 0.25–0.42), and area under receiver operating characteristic (AUROC) of 0.81 (95% CI 0.77–0.84). T-SPOT.TB had sensitivity of 0.74 (95% CI 0.71–0.78), specificity of 0.71 (95% CI 0.49–0.86), DOR of 6.96 (95% CI 2.31–20.98), positive LR of 2.53 (95% CI 1.26–5.07), negative LR of 0.36 (95% CI 0.24–0.55), and AUROC of 0.77 (95% CI 0.73–0.80). The specificity seemed lower in the subgroup analyses of studies from high tuberculosis burden counties compared to the studies from low tuberculosis burden.

Conclusion

IGRAs do have insufficient diagnostic performance for SNPTB. However, the tests are still helpful to exclude tuberculosis among patients with low pre-test probability.

Registry: PROSPERO: CRD42021274653.

Diagnostic Performance of a Novel CXCL10 mRNA Release Assay for Mycobacterium tuberculosis Infection

One-fourth of the world’s population has been infected with Mycobacterium tuberculosis (M.tb). Although interferon-gamma release assays (IGRAs) have been shown to be valid methods for identifying M.tb infection and auxiliary methods for diagnosis of active tuberculosis (TB), lower sensitivity and higher indeterminate rate were often detected among immunosuppressed patients. IP-10 was an alternative biomarker due to the higher expression level after M.tb antigen stimulation, but whether CXCL10 mRNA (the gene that transcribes for the IP-10 protein) can be used as a target for M.tb infection diagnosis was limited. Therefore, we aimed to evaluate the performance of a novel M.tb-specific CXCL10 mRNA release assay in diagnosis of M.tb infection. Suspected TB patients and healthy controls were prospectively recruited between March 2018 and November 2019 from three hospitals in China. CXCL10 mRNA release assay and traditional interferon-gamma release assay (T-SPOT.TB) were simultaneously performed on peripheral blood. Of the 1,479 participants enrolled in the study, 352 patients with definite TB and 153 healthy controls were analyzed. CXCL10 mRNA release assay provided a sensitivity of 93.9% (95% CI = 90.8–96.2%) and a specificity of 98.0% (95% CI = 94.3–99.6%) in the diagnosis of M.tb infection, respectively, while T-SPOT.TB gave a sensitivity of 94.5% (95% CI = 91.5–96.6%) and a specificity of 100% (95% CI = 97.6–100.0%) in the diagnosis of M.tb infection, respectively. The diagnostic performance of CXCL10 mRNA release assay was consistent with T-SPOT.TB, with a total coincidence rate of 95.0% (95% CI = 93.0–96.9%) and a Cohen’s kappa value of 0.89 (0.84–0.93, p < 0.001). However, among TB patients with HIV co-infection (n = 14), CXCL10 mRNA release assay presented significantly higher positive rate [92.9% (66.1–99.8%) vs. 61.5% (31.6–86.1%), p = 0.029] than those of T-SPOT.TB. These results suggested that M.tb-specific CXCL10 mRNA was a novel and useful target in the diagnosis of M.tb infection.

Diagnostic Value of Interferon-Gamma Release Assays for Tuberculosis in the Immunocompromised Population

Interferon-gamma release assays (IGRAs) are widely used in the diagnosis of Mycobacterium tuberculosis (M. tuberculosis) infection by detecting interferon-γ released by previously sensitized T-cells in-vitro. Currently, there are two assays based on either enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunospot (ELISPOT) technology, with several generations of products available. The diagnostic value of IGRAs in the immunocompromised population is significantly different from that in the immunocompetent population because their results are strongly affected by the host immune function. Both physiological and pathological factors can lead to an immunocompromised situation. We summarized the diagnostic value and clinical recommendations of IGRAs for different immunocompromised populations, including peoplewith physiological factors (pregnant and puerperal women, children, and older people), as well as people with pathological factors (solid organ transplantation recipients, combination with human immunodeficiency virus infection, diabetes mellitus, end-stage renal disease, end-stage liver disease, and chronic immune-mediated inflammatory diseases). Though the performance of IGRAs is not perfect and often requires a combination with other diagnostic strategies, it still has some value in the immunocompromised population. Hopefully, the newly developed IGRAs could better target this population.

Differentiating between active and latent tuberculosis with chest computed tomography

PURPOSE

The purpose of this study was to evaluate the capabilities of chest computed tomography (CT) in distinguishing between active and latent tuberculosis in patients positive for interferon-gamma release assay (IGRA) testing, and to compare the performance of CT with that of quantitative IGRA testing in a low incidence setting.

MATERIALS AND METHODS

Patients with latent or active tuberculosis define by an IGRA positive test were retrospectively recruited. Sensitivity, specificity and accuracy were determined for CT variables and quantitative IGRA results. Final diagnosis of active tuberculosis was based on clinical data and microbiological culture. Univariable and multivariable analyses were performed using logistic regression model to identify CT variables associated with the diagnosis of active tuberculosis.

RESULTS

A total of 92 patients with positive IGRA results who underwent CT examination were included. There were 54 men and 38 women with a mean age of 53.5±18 (SD) years (range: 40-68 years). Of them, 22 patients (24%) had positive Mycobacterium tuberculosis culture and 70 (76%) had latent tuberculosis. Among CT variables, consolidation had the greatest sensitivity (77%; 95%CI: 60-95%) and "tree-in-bud" the greatest specificity (97%; 95% CI: 93-100%) for the diagnosis of active tuberculosis. At univariable analysis "tree-in-bud", splenic calcification and non-calcified lung nodules were the significant variables independently associated with active tuberculosis. At multivariable analysis, the adjusted odds ratio of "tree-in-bud" was 42.91 (95% CI: 5.62-327.42). Using an optimal threshold of 51 spots, quantitative IGRA yielded 64% sensitivity (95% CI: 44-84%) and 61% specificity (95% CI: 50-73%) for the diagnosis of active tuberculosis.

CONCLUSIONS

In a low incidence setting, chest CT, especially when "tree-in-bud" pattern is present, is superior to quantitative IGRA testing to identify patients with active tuberculosis among those with positive IGRA testing.

Role of interferon gamma release assay in the diagnosis and management of Mycobacterium tuberculosis-associated uveitis: a review

Tuberculosis (TB)-associated uveitis is a common cause of infectious uveitis in the developing world. Diagnosis of TB uveitis remains a challenge. The role of interferon gamma release assays (IGRAs) is uncertain. Herein we summarise the available literature on the utility of IGRAs in the diagnosis and management of TB uveitis. We searched PubMed database from 1 August 2010 to 31 July 2020 using the following keywords alone and in combination: 'interferon-gamma release assay', 'QuantiFERON', 'T-SPOT.TB', 'TB uveitis', 'serpiginous like choroiditis', 'tuberculoma', 'TB vasculitis', 'TB panuveitis' and 'ocular tuberculosis'. Data from 58 relevant studies were collated. The review is focused on currently marketed versions of IGRA tests: QuantiFERON-TB Gold In-Tube assay, QuantiFERON-TB Gold Plus assay (QFT-Plus) and T-SPOT.TB. We found limited evidence regarding the diagnostic utility of IGRA in patients with uveitis. No study was identified evaluating the newer QFT test-the QFT-Plus-in patients with uveitis. Similarly, there is lack of data directly comparing QFT-Plus with T-SPOT.TB specifically for the diagnosis of TB uveitis.

Evaluation of the performance of QuantiFERON®-TB Gold plus test in active tuberculosis patients

The aim was to evaluate the sensitivity and the possible factors affecting the sensitivity of the QuantiFERON®-TB Gold Plus (QFT-Plus) assay in culture-positive active TB (Tuberculosis) patients, to investigate the possible causes of negative and indeterminate results in active TB patients, and to compare the QFT-Plus results of active TB patients and latent tuberculosis infection (LTBI) cases. The QFT-Plus assay was performed in 46 active TB patients and 64 LTBI. The sensitivity of the test was found as 79.5% in all culture-positive patients, 72.7% in the immunocompromised patients, and 86.4% in the non-immunocompromised patients. Compared to active TB, individuals with LTBI had a lower T-cell response and lower IFN-ɣ concentrations. It was determined that the immunocompromisation reduced the sensitivity of the test and the secreted IFN-ɣ concentrations and increased the indeterminate results in patients with active TB. There was no difference in secreted IFN-ɣ concentrations between M. tuberculosis clones, but higher IFN-ɣ concentrations in patients infected with M. tuberculosis strains compared to patients infected with zoonotic strains. Compared with active TB, response to “only to TB2” was significantly higher in LTBI. In conclusion, it was concluded that TB2 tube increased sensitivity in LTBI but may not contribute to sensitivity in active TB.

Evaluation of risk factors for false-negative results with an antigen-specific peripheral blood-based quantitative T cell assay (T-SPOT®. TB) in the diagnosis of active tuberculosis: A large-scale retrospective study in China

Objective To investigate the diagnostic efficacy of an interferon-γ release assay, T-SPOT^®. TB, for diagnosing active tuberculosis (TB) and to identify risk factors for false-negative results. Methods This retrospective study enrolled consecutive patients with active TB and with non-TB respiratory diseases to evaluate the risk factors for false-negative results when using the T-SPOT^®. TB assay for the diagnosis of active TB. Patients with active TB were categorized as having confirmed pulmonary TB, clinically diagnosed pulmonary TB or extrapulmonary TB (EPTB). Results This study analysed 4964 consecutive patients; 2425 with active TB and 2539 with non-TB respiratory diseases. Multivariate logistic regression analyses identified the following five factors that were all associated with an increased false-negative rate with the T-SPOT^®. TB assay: increased age (odds ratio [OR] 1.018; 95% confidence interval [CI] 1.013, 1.024); decreased CD8+ count (OR 0.307; 95% CI 0.117, 0.803); negative sputum acid-fast bacilli (AFB) smear staining (OR 1.821; 95% CI 1.338, 2.477); negative mycobacterial cultures (OR 1.379; 95% CI 1.043, 1.824); and absence of EPTB (OR 1.291; 95% CI 1.026, 1.623). Conclusions Increased age, decreased CD8+ count, negative sputum AFB smear results, negative sputum mycobacterial cultures and absence of EPTB might lead to an increased false-negative rate when using the T-SPOT^®. TB assay.

Impact of diabetes mellitus on indeterminate results of the QuantiFERON TB Gold In-Tube test: A propensity score matching analysis

Background

The sensitivity of interferon-gamma release assays (IGRAs) in the detection of Mycobacterium tuberculosis infection could be affected by conditions of immune dysregulation. For this reason, diabetes mellitus (DM) may increase the frequency of indeterminate results of IGRAs. However, there have been inconsistent reports of role of DM on indeterminate IGRA results.

Methods

We retrospectively reviewed all patients who underwent QuantiFERON-TB Gold In-Tube testing (QFT-GIT) at Chonnam National University Hospital. We collected the clinical and laboratory data of these patients.

Results

Of all 3,391 subjects, 1,265 (37.3%) had a positive QFT-GIT result, 266 (7.8%) had an indeterminate result, and 1,860 (54.9%) had a negative result. The mean age was 54.8 ± 18.1 years and 55.0% of the patients were male. There were 512 (15.1%) patients with DM. Multivariable analysis revealed that systemic corticosteroid use, tuberculosis, lymphocytopenia, low serum albumin, and high serum C-reactive protein (CRP) levels were significantly associated with indeterminate QFT-GIT results. However, DM was not associated with indeterminate QFT-GIT results (adjusted odds ratio, 0.98; 95% confidence interval, 0.69–1.41; P = 0.939). After propensity score matching, DM was not associated with indeterminate results of QFT-GIT.

Conclusion

In this large cohort study, DM does not affect the incidence of indeterminate results of QFT-GIT.

Diabetes and Tuberculosis

The increase in type 2 diabetes mellitus (DM) patients in countries where tuberculosis (TB) is also endemic has led to the reemerging importance of DM as a risk factor for TB. DM causes a 3-fold increase in TB risk and a 2-fold increase in adverse TB treatment outcomes. Given the sheer numbers of DM patients worldwide, there are now more TB patients with TB-DM comorbidity than TB-HIV coinfection. There is an urgent need to implement strategies for TB prevention and control among the millions of DM patients exposed to Mycobacterium tuberculosis. This chapter summarizes the current epidemiological, clinical, and immunological knowledge on TB and DM and their clinical and public health implications. These include the underlying mechanisms for TB risk in DM patients and their clinical and sociodemographic characteristics that distinguish them from TB patients without DM. TB-DM comorbidity is posing a new challenge for integrating the short-term care for TB with the long-term care for DM, particularly in low- and middle-income countries.

The performance of T-cell Xtend reagent in increasing blood storage times for interferon gamma release assays

BACKGROUND

T-cell Xtend (TCX) was introduced to extend the blood storage time for T-SPOT.TB test, a widely used commercial interferon gamma release assay (IGRA) for rapid in vitro tuberculosis.

METHODS

A total of 99 Uyghur suspected tuberculosis patients were recruited in this study. T-SPOT.TB test was performed with fresh blood (controls), 36 hours delayed blood and delayed and TCX-treated (at 36 hours) blood from each patient, respectively.

RESULTS

White blood cells and lymphocytes proportion in peripheral blood mononuclear cells s and spot-forming cells in positive control wells decreased significantly in delayed blood samples when compared with controls, while this decrease was not detected in TCX-treated group. In the 58 patients with paired T-SPOT.TB results of three groups of samples, a higher positive rate was observed in TCX-treated group than both in controls and untreated group (41.4% vs 37.9% and 25.9%). The concordance of T-SPOT.TB results between the treated group and controls was 0.856, whereas the agreement between controls and untreated group was unsatisfactory (0.649). In the 23 elderly patients (>70 years old) with paired T-SPOT.TB results of controls and TCX group, treated group showed a non-significant trend toward higher positive rate than controls (43.5% vs 26.1%, P=.22). Meanwhile, TCX treatment reduced the risk of false negative T-SPOT.TB results in the elderly population.

CONCLUSION

Deterioration of blood sample caused by long storage time can be neutralized by TCX treatment. The results provide data for the utility of TCX in a novel population and in Asian region, and reveal the potential of TCX to improve the accuracy of T-SPOT.TB test in elderly population.

Interferon-Gamma Release Assays for the Diagnosis of Tuberculosis: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVE

We conducted a systematic review and meta-analysis to compare the accuracy of the interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST) for the diagnosis of Mycobacterium tuberculosis infection.

METHODS

We systematically searched PubMed, Embase, Cochrane library, and Web of Science databases for relevant published studies in recent decades and calculated pooled estimated sensitivities, specificities, DOR, and SROC curve of the QFT-IT, T-SPOT and TST. Random-effects models were used to assess estimates from studies with significant heterogeneity. Moreover, area under the curve was used to evaluate the accuracy of the tests.

RESULTS

Overall, 9 studies for QFT-IT, 12 studies for T-SPOT, and 16 studies for TST involving 3586 participants were included in this analysis. We found that sensitivities of the QFT-IT, T-SPOT, and TST were respectively 0.842 (95 % CI 0.811-0.870), 0.840 (95 % CI 0.814-0.864), and 0.665 (CI 0.635-0.693); specificities were respectively 0.745 (95 % CI 0.715-0.775), 0.658 (95 % CI 0.621-0.693), and 0.633 (CI 0.605-0.661); positive likelihood ratios were respectively 3.652 (95 % CI 2.180-6.117), 2.196 (95 % CI 1.727-2.794), and 1.825 (95 % CI 1.351-2.464); negative likelihood ratios were respectively 0.212 (95 % CI 0.109-0.414), 0.246 (95 % CI 0.161-0.377), and 0.556 (95 % CI 0.385-0.804); the SROC curves were 19.205, 10.397, and 3.810.

CONCLUSIONS

The two IGRAs showed better performance than TST for the diagnosis of the tuberculosis. However, neither of them showed stability in the diagnosis of TB.

Factors that Predict Negative Results of QuantiFERON-TB Gold In-Tube Test in Patients with Culture-Confirmed Tuberculosis: A Multicenter Retrospective Cohort Study

BACKGROUND

Interferon-γ release assays such as the QuantiFERON-TB Gold In-Tube Test (QFT-GIT) are designed to detect Mycobacterium tuberculosis infections, whether latent or manifesting as disease. However, a substantial number of persons with culture-confirmed tuberculosis (TB) have negative QFT-GITs. Information on host factors contributing to false-negative and indeterminate results are limited.

METHODS

A multicenter retrospective cohort study was performed with 1,264 culture-confirmed TB patients older than 18 years who were subjected to the QFT-GIT at one of the six hospitals between May 2007 and February 2014. Patients with human immunodeficiency virus infection were excluded. Clinical and laboratory data were collected in South Korea.

RESULTS

Of all patients, 87.6% (1,107/1,264) were diagnosed with pulmonary TB and 12.4% (157/1,264) with extrapulmonary TB. The rate of negative results was 14.4% (182/1,264). The following factors were highly correlated with false-negative results in the QFT-GIT: advanced age (age ≥ 65 years, odds ratio [OR] 1.57, 95% confidence interval [CI] 1.03-2.39), bilateral disease as determined by chest radiography (OR 1.75, 95% CI 1.13-2.72), malignancy (OR 2.42, 95% CI 1.30-4.49), and lymphocytopenia (total lymphocyte count < 1.0 × 109/L, OR 1.86, 95% CI 1.21-2.87).

CONCLUSIONS

Consequently, QFT-GIT results need to be interpreted with caution in patients with these host risk factors such as the elderly, bilateral disease on chest radiography, or malignancy, or lymphocytopenia.

Impact of diabetes on the natural history of tuberculosis

Tuberculosis (TB) is the number one bacterial killer worldwide and the current increase in type 2 diabetes mellitus patients (DM), particularly in countries where TB is also endemic, has led to the re-emerging importance of DM2 as a risk factor for TB. There is an urgent need to implement strategies for TB prevention among the millions of DM patients exposed to Mycobacterium tuberculosis (Mtb) worldwide, but knowledge is limited on how and when DM2 alters the natural history of this infection. In this review we summarize the current epidemiological, clinical and immunologic studies on TB and DM and discuss the clinical and public health implications of these findings. Specifically, we evaluate the mechanisms by which DM patients have a higher risk of Mtb infection and TB development, present with signs and symptoms indicative of a more infectious TB infection, and are more likely to have adverse TB treatment outcomes, including death. Emphasis is placed on type 2 DM given its higher prevalence in contemporary times, but the underlying role of hyperglycemia and of type 1 DM is also discussed.

Tuberculin skin test versus interferon-gamma release assays for the diagnosis of tuberculosis infection

OBJECTIVE

Accurate detection of latent tuberculosis infection (LTBI) is becoming increasingly important due to the increasing use of immunosuppressive medications and the human immunodeficiency epidemic, which have increased the risk for reactivation to active tuberculosis (TB) infection. LTBI is detected by tuberculin skin test (TST) and interferon-gamma release assays (IGRAs). The latter include T-SPOT(®).TB (Oxford Immunotec) and QuantiFERON(®)-TB Gold In-Tube (QFT-GIT; Cellestis). We examined the value of TST versus IGRAs in the diagnosis of TB infection by meta-analysis based on data derived from a systematic literature review.

METHODS

PubMed was searched for articles in English published between January 2010 and July 2012 in which TST and IGRA were performed simultaneously in individuals with and without active TB infection. A random effect model meta-analysis was performed to determine pooled sensitivity and specificity values for TST, T-SPOT.TB, and QFT-GIT. Owing to the absence of a gold standard for the diagnosis of LTBI, active TB infection was used as a surrogate for LTBI.

RESULTS

Nineteen studies were included. T-SPOT.TB was significantly more sensitive [90% (95% confidence interval: 85-95) versus 64% (46-81)] than TST. The specificity of T-SPOT.TB was higher than the specificity of TST, but there was overlap between confidence intervals [77% (68-85) versus 57% (41-72)]. QFT-GIT seemed to be more sensitive than TST [75% (61-86) versus 64% (48-78)] but similarly specific [71% (62-86) versus 70% (57-81)].

CONCLUSIONS

IGRAs, especially T-SPOT.TB, are more effective at detecting TB infection than TST. Despite their higher cost, they have added value and can be requested in addition to TST.

Tuberculosis in patients with haematological malignancies

Tuberculosis (TB) is an infectious disease that causes more than 1 million deaths worldwide every year. In addition, it is estimated that one third of the world population is infected with M. tuberculosis in a latent state, which involves an eventual risk of progressing to active TB disease. Patients with immunodeficiencies, such as those suffering from haematological malignancies, have a greater risk of progressing to TB disease once infected. It is estimated that the Relative Risk of TB disease in patients with hematologic malignancies is 2–40 times that of the general population. The diagnosis of TB in these patients is often challenging as they often present clinical characteristics that are distinct to those of patients without any other underlying disease. Mortality due to TB is higher. Therefore, it is recommended to diagnose latent TB infection and consider preventive therapy that could avoid the progression from a latent state to active TB disease. There are currently two methods for diagnosing latent TB infection: the Tuberculin Skin Test (TST) and the Interferon-Gamma Release Assays (IGRA). Due to the lack of sensitivity in patients with immunodeficient conditions, a combined TST-IGRA testing is probably the best way for latent TB diagnosis in order to gain sensitivity. Treatment of latent TB infection and TB disease should follow the general principles to that in the general population.

Evaluation of an enzyme-linked immunospot assay for the immunodiagnosis of atypical spinal tuberculosis (atypical clinical presentation/atypical radiographic presentation) in China

Background

Methods

Results

Conclusions

Predictive factors for tuberculosis in patients with a TB-PCR-negative bronchial aspirate

PURPOSE

Pulmonary tuberculosis (PTB), with a tuberculosis (TB)-polymerase chain reaction (PCR)-negative bronchial aspirate (BA), but a positive culture result is often encountered in clinical practice. However, limited data are available concerning clinical judgment in patients with suspected PTB and a TB-PCR-negative BA pending culture results. The present study aimed to identify predictors for PTB in patients with a TB-PCR-negative BA.

METHODS

A retrospective study was conducted on patients who had undergone a bronchoscopy because of suspected PTB. Clinical, laboratory, and computed tomography (CT) findings were investigated in PTB patients with TB-PCR-negative but positive culture BA results, and non-PTB patients with a radiographic lesion comparable to the former.

RESULTS

Of 250 patients screened, 31 (12 %) were diagnosed with PTB by positive culture results only. Of these 31 patients, 30 (97 %) had a lesion within one-third of the hemithorax as determined by chest radiography. In the final analysis of 30 PTB and 65 non-PTB patients with comparable radiographic lesions, a positive QuantiFERON-TB Gold In-Tube (QFT) result was independently associated with an increased risk of a positive TB culture. CT findings of consolidation were a negative predictor for PTB. Patients with a negative QFT result and consolidation had a negative predictive value of 95 % for PTB, while patients with a positive QFT result and nodular CT abnormalities without consolidation had a positive predictive value of 86 % for PTB.

CONCLUSION

The simple combination of CT findings of consolidation and QFT test results may help clinicians to refine decision-making in patients with a TB-PCR-negative BA.