False-negative results by enzyme-linked immunospot assay for interferon-gamma among patients with culture-confirmed tuberculosis

Resuming anti-TNF therapy after development of miliary tuberculosis in Behcet's disease-related uveitis: a case report

PURPOSE

There is no consensus concerning restarting anti-tumour necrosis factor (TNF)-α therapy for uveitis after treatment for active tuberculosis (TB). We report a case of Behcet disease (BD) in which treatment with TNF inhibitor was successfully resumed after treatment for miliary TB.

CASE REPORT

A 48-year-old Japanese male was treated for uveitis of unknown aetiology in the left eye at a general ophthalmology clinic. He was referred to Department of Ophthalmology, Tokyo Medical University Hospital because of macula oedema (ME) not responding to prednisolone (PSL) 20 mg. BD was diagnosed based on fluorescein angiographic findings of diffuse retinal vasculitis characteristic of BD, recurrent oral aphthous ulcer, erythema nodosum-like rash in his legs, and HLA-A26 positivity. After a screening test, adalimumab (ADA) was started as steroid-sparing therapy. Eight months after starting ADA, the patient was diagnosed with miliary TB. ADA and PSL were discontinued immediately due to TB. Anti-TB treatment was completed after 6 months based on clinical improvement, although T-SPOT.TB was still positive. Infliximab with isoniazid was started due to relapse of ME, worsened vitreous haze, and worsened visual acuity in his left eye. Subsequently, his ocular symptoms subsided and there was no relapse of TB.

CONCLUSION

This case suggests that in patients with BD who have discontinued anti-TNF therapy due to miliary TB, restarting anti-TNF therapy may be a therapeutic option after TB has been treated appropriately with careful monitoring for relapse.

Development of diagnostic algorithm using machine learning for distinguishing between active tuberculosis and latent tuberculosis infection

BACKGROUND

The discrimination between active tuberculosis (ATB) and latent tuberculosis infection (LTBI) remains challenging. The present study aims to investigate the value of diagnostic models established by machine learning based on multiple laboratory data for distinguishing Mycobacterium tuberculosis (Mtb) infection status.

METHODS

T-SPOT, lymphocyte characteristic detection, and routine laboratory tests were performed on participants. Diagnostic models were built according to various algorithms.

RESULTS

A total of 892 participants (468 ATB and 424 LTBI) and another 263 participants (125 ATB and 138 LTBI), were respectively enrolled at Tongji Hospital (discovery cohort) and Sino-French New City Hospital (validation cohort). Receiver operating characteristic (ROC) curve analysis showed that the value of individual indicator for differentiating ATB from LTBI was limited (area under the ROC curve (AUC) < 0.8). A total of 28 models were successfully established using machine learning. Among them, the AUCs of 25 models were more than 0.9 in test set. It was found that conditional random forests (cforest) model, based on the implementation of the random forest and bagging ensemble algorithms utilizing conditional inference trees as base learners, presented best discriminative power in segregating ATB from LTBI. Specially, cforest model presented an AUC of 0.978, with the sensitivity of 93.39% and the specificity of 91.18%. Mtb-specific response represented by early secreted antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) spot-forming cell (SFC) in T-SPOT assay, as well as global adaptive immunity assessed by CD4 cell IFN-γ secretion, CD8 cell IFN-γ secretion, and CD4 cell number, were found to contribute greatly to the cforest model. Superior performance obtained in the discovery cohort was further confirmed in the validation cohort. The sensitivity and specificity of cforest model in validation set were 92.80% and 89.86%, respectively.

CONCLUSIONS

Cforest model developed upon machine learning could serve as a valuable and prospective tool for identifying Mtb infection status. The present study provided a novel and viable idea for realizing the clinical diagnostic application of the combination of machine learning and laboratory findings.

Serial interferon-gamma release assay in lung cancer patients receiving immune checkpoint inhibitors: a prospective cohort study

Recent advancements in cancer immunotherapy using immune checkpoint inhibitors (ICIs) have received considerable attention. Although advantageous, ICI therapies cause unique immune-related adverse events (irAEs) in some patients. Moreover, infectious diseases, such as tuberculosis, have been recognized as emerging concerns during immunotherapy. We aimed to evaluate the interferon-gamma release assay (IGRA) conversion rate and active tuberculosis incidence during immunotherapy to elucidate the incidence of tuberculosis reactivation after ICI therapy induction.We prospectively assessed IGRA results in lung cancer patients who received ICI monotherapy before ICI treatment and at 6 and 12 months after ICI treatment. We also assessed computed tomography findings to determine the presence of active tuberculosis when positive IGRA results were obtained. The ICIs used were nivolumab, pembrolizumab, atezolizumab, and durvalumab.In all, 178 patients were prospectively recruited between March 2017 and March 2020. Of these, 123 completed serial IGRAs, of whom 18, 101, and 4, respectively, had positive, negative, and indeterminate IGRAs at baseline. Three and four patients, respectively, showed IGRA reversion and conversion during immunotherapy. One patient with a sustained, stable positive IGRA and one with IGRA conversion developed active pulmonary tuberculosis during immunotherapy.We found that 3.3% and 1.6% of the patients developed IGRA conversion and active tuberculosis, respectively. Of the four patients who developed IGRA conversion, one developed active pulmonary tuberculosis during immunotherapy. Another patient with sustained, stable positive IGRA developed active tuberculosis. Physicians should be alert to tuberculosis development during ICI therapy, and IGRA testing is a useful tool to assess the risk of developing active tuberculosis.

Combination of HLA-DR on Mycobacterium tuberculosis-Specific Cells and Tuberculosis Antigen/Phytohemagglutinin Ratio for Discriminating Active Tuberculosis From Latent Tuberculosis Infection

Background

Novel approaches for tuberculosis (TB) diagnosis, especially for distinguishing active TB (ATB) from latent TB infection (LTBI), are urgently warranted. The present study aims to determine whether the combination of HLA-DR on Mycobacterium tuberculosis (MTB)-specific cells and TB antigen/phytohemagglutinin (TBAg/PHA) ratio could facilitate MTB infection status discrimination.

Methods

Between June 2020 and June 2021, participants with ATB and LTBI were recruited from Tongji Hospital (Qiaokou cohort) and Sino-French New City Hospital (Caidian cohort), respectively. The detection of HLA-DR on MTB-specific cells upon TB antigen stimulation and T-SPOT assay were simultaneously performed on all subjects.

Results

A total of 116 (54 ATB and 62 LTBI) and another 84 (43 ATB and 41 LTBI) cases were respectively enrolled from Qiaokou cohort and Caidian cohort. Both HLA-DR on IFN-γ⁺TNF-α⁺ cells and TBAg/PHA ratio showed discriminatory value in distinguishing between ATB and LTBI. Receiver operator characteristic (ROC) curve analysis showed that HLA-DR on IFN-γ⁺TNF-α⁺ cells produced an area under the ROC curve (AUC) of 0.886. Besides, TBAg/PHA ratio yield an AUC of 0.736. Furthermore, the combination of these two indicators resulted in the accurate discrimination with an AUC of 0.937. When the threshold was set as 0.36, the diagnostic model could differentiate ATB from LTBI with a sensitivity of 92.00% and a specificity of 81.82%. The performance obtained in Qiaokou cohort was further validated in Caidian cohort.

Conclusions

The combination of HLA-DR on MTB-specific cells and TBAg/PHA ratio could serve as a robust tool to determine TB disease states.

Lymphocyte-Related Immunological Indicators for Stratifying Mycobacterium tuberculosis Infection

Background

Easily accessible tools that reliably stratify Mycobacterium tuberculosis (MTB) infection are needed to facilitate the improvement of clinical management. The current study attempts to reveal lymphocyte-related immune characteristics of active tuberculosis (ATB) patients and establish immunodiagnostic model for discriminating ATB from latent tuberculosis infection (LTBI) and healthy controls (HC).

Methods

A total of 171 subjects consisted of 54 ATB, 57 LTBI, and 60 HC were consecutively recruited at Tongji hospital from January 2019 to January 2021. All participants were tested for lymphocyte subsets, phenotype, and function. Other examination including T-SPOT and microbiological detection for MTB were performed simultaneously.

Results

Compared with LTBI and HC, ATB patients exhibited significantly lower number and function of lymphocytes including CD4⁺ T cells, CD8⁺ T cells and NK cells, and significantly higher T cell activation represented by HLA-DR and proportion of immunosuppressive cells represented by Treg. An immunodiagnostic model based on the combination of NK cell number, HLA-DR⁺CD3⁺ T cells, Treg, CD4⁺ T cell function, and NK cell function was built using logistic regression. Based on receiver operating characteristic curve analysis, the area under the curve (AUC) of the diagnostic model was 0.920 (95% CI, 0.867-0.973) in distinguishing ATB from LTBI, while the cut-off value of 0.676 produced a sensitivity of 81.48% (95% CI, 69.16%-89.62%) and specificity of 91.23% (95% CI, 81.06%-96.20%). Meanwhile, AUC analysis between ATB and HC according to the diagnostic model was 0.911 (95% CI, 0.855-0.967), with a sensitivity of 81.48% (95% CI, 69.16%-89.62%) and a specificity of 90.00% (95% CI, 79.85%-95.34%).

Conclusions

Our study demonstrated that the immunodiagnostic model established by the combination of lymphocyte-related indicators could facilitate the status differentiation of MTB infection.

Lymphocyte Non-Specific Function Detection Facilitating the Stratification of Mycobacterium tuberculosis Infection

Background

Inadequate tuberculosis (TB) diagnostics, especially for discrimination between active TB (ATB) and latent TB infection (LTBI), are major hurdle in the reduction of the disease burden. The present study aims to investigate the role of lymphocyte non-specific function detection for TB diagnosis in clinical practice.

Methods

A total of 208 participants including 49 ATB patients, 64 LTBI individuals, and 95 healthy controls were recruited at Tongji hospital from January 2019 to October 2020. All subjects were tested with lymphocyte non-specific function detection and T-SPOT assay.

Results

Significantly positive correlation existed between lymphocyte non-specific function and phytohemagglutinin (PHA) spot number. CD4⁺ T cell non-specific function showed the potential for differentiating patients with negative T-SPOT results from those with positive T-SPOT results with an area under the curve (AUC) of 0.732 (95% CI, 0.572-0.893). The non-specific function of CD4⁺ T cells, CD8⁺ T cells, and NK cells was found significantly lower in ATB patients than in LTBI individuals. The AUCs presented by CD4⁺ T cell non-specific function, CD8⁺ T cell non-specific function, and NK cell non-specific function for discriminating ATB patients from LTBI individuals were 0.845 (95% CI, 0.767-0.925), 0.770 (95% CI, 0.683-0.857), and 0.691 (95% CI, 0.593-0.789), respectively. Application of multivariable logistic regression resulted in the combination of CD4⁺ T cell non-specific function, NK cell non-specific function, and culture filtrate protein-10 (CFP-10) spot number as the optimally diagnostic model for differentiating ATB from LTBI. The AUC of the model in distinguishing between ATB and LTBI was 0.939 (95% CI, 0.898-0.981). The sensitivity and specificity were 83.67% (95% CI, 70.96%-91.49%) and 90.63% (95% CI, 81.02%-95.63%) with the threshold as 0.57. Our established model showed superior performance to TB-specific antigen (TBAg)/PHA ratio in stratifying TB infection status.

Conclusions

Lymphocyte non-specific function detection offers an attractive alternative to facilitate TB diagnosis. The three-index diagnostic model was proved to be a potent tool for the identification of different events involved in TB infection, which is helpful for the treatment and management of patients.

Combination of prealbumin and tuberculosis-specific antigen/phytohemagglutinin ratio for discriminating active tuberculosis from latent tuberculosis infection

BACKGROUND

Given that there is no rapid and effective method for distinguishing active tuberculosis (ATB) from latent tuberculosis infection (LTBI), the discrimination between these two statuses remains challenging. This study sought to investigate the value of nutritional indexes and tuberculosis-specific antigen/phytohemagglutinin ratio (TBAg/PHA ratio) for distinguishing ATB from LTBI.

METHODS

Participants were consecutively recruited based on positive T-SPOT.TB results between January 2018 and January 2020. ATB was diagnosed by positive mycobacterial culture and/or positive GeneXpert MTB/RIF, with clinical symptoms and radiological characteristics suggestive of ATB. Individuals with positive T-SPOT.TB but without the evidence of ATB were defined as LTBI. Patients younger than 17 years and undergoing anti-TB treatment were excluded.

RESULTS

A total of 709 (312 ATB and 397 LTBI) and another 309 (120 ATB and 189 LTBI) subjects were respectively recruited from Tongji Hospital (Qiaokou cohort) and Sino-French New City Hospital (Caidian cohort). The level of prealbumin was significantly lower in ATB than in LTBI. With a cut-off value of 139 mg/L, the sensitivity and specificity of prealbumin in distinguishing ATB from LTBI were 50.96% (45.41%-56.51%) and 91.69% (88.97%-94.40%). Meanwhile, TBAg/PHA ratio was found statistically higher in ATB compared with LTBI. If using the threshold of 0.29, the sensitivity and specificity of TBAg/PHA ratio were 65.71% (60.44%-70.97%) and 90.93% (88.11%-93.76%), respectively. Moreover, the combination of prealbumin and TBAg/PHA ratio (obtaining by diagnostic model) yielded better specificity (90.18%, [87.25%-93.10%]) and sensitivity (87.18%, [83.47%-90.89%]), while the clinical utility index (CUI) positive and CUI negative were respectively 0.76 and 0.81. After anti-TB treatment, TBAg/PHA ratio was declined while the level of prealbumin was restored (Wilcoxon test, P < 0.001). Furthermore, the performance of diagnostic model obtained in Qiaokou cohort was confirmed in Caidian cohort.

CONCLUSIONS

The diagnostic model based on combination of prealbumin and TBAg/PHA ratio is a rapid and accurate tool for discriminating ATB from LTBI.

A combination of iron metabolism indexes and tuberculosis-specific antigen/phytohemagglutinin ratio for distinguishing active tuberculosis from latent tuberculosis infection

BACKGROUND

Discriminating active tuberculosis (ATB) from latent tuberculosis infection (LTBI) remains challenging. This study aimed to investigate a diagnostic model based on a combination of iron metabolism and the TB-specific antigen/phytohemagglutinin ratio (TBAg/PHA ratio) in T-SPOT.TB assay for differentiation between ATB and LTBI.

METHODS

A total of 345 participants with ATB (n=191) and LTBI (n=154) were recruited based on positive T-SPOT.TB results at Tongji hospital between January 2017 and January 2020. Iron metabolism analysis was performed simultaneously. A diagnostic model for distinguishing ATB from LTBI was established according to multivariate logistic regression.

RESULTS

The TBAg/PHA ratio showed 64.00% sensitivity and 90.10% specificity in distinguishing ATB from LTBI when a threshold of 0.22 was used. All iron metabolism biomarkers in the ATB group were significantly different from those in the LTBI group. Specifically, serum ferritin and soluble transferrin receptor in ATB were significantly higher than LTBI. On the contrary, serum iron, transferrin, total iron binding capacity, and unsaturated iron binding capacity in ATB were significantly lower than LTBI. The combination of iron metabolism indicators accurately predicted 60.00% of ATB cases and 91.09% of LTBI subjects, respectively. Moreover, the combination of iron metabolism indexes and TBAg/PHA ratio resulted in a sensitivity of 88.80% and specificity of 90.10%. Furthermore, the performance of models established in the Qiaokou cohort was confirmed in the Caidian cohort.

CONCLUSIONS

The data suggest that the combination of iron metabolism indexes and TBAg/PHA ratio could serve as a biomarker to distinguish ATB from LTBI in T-SPOT-positive individuals.

Combination of mean spot sizes of ESAT-6 spot-forming cells and modified tuberculosis-specific antigen/phytohemagglutinin ratio of T-SPOT.TB assay in distinguishing between active tuberculosis and latent tuberculosis infection

OBJECTIVES

Distinguishing between active tuberculosis (ATB) and latent tuberculosis infection (LTBI) remains challenging.

METHODS

The modified T-SPOT.TB assay was performed in 499 participants (243 ATB and 256 LTBI) and another 322 participants (162 ATB and 160 LTBI) who were diagnosed in Qiaokou (training) and Caidian (validation) cohort respectively.

RESULTS

The mean spot sizes (MSS) of early secreted antigenic target 6 (ESAT-6) spot-forming cells (SFC) of T-SPOT.TB assay in ATB patients was significantly higher than that in LTBI individuals. 1.0 × 10⁵ was the optimal number of cells added to phytohaemagglutinin (PHA) well for obtaining more accurate TB-specific antigen to phytohaemagglutinin (TBAg/PHA) ratio. The area under the curve of the diagnostic model by combination of ESAT-6 SFC MSS and modified TBAg/PHA ratio in distinguishing ATB from LTBI was 0.959 in training cohort, with a sensitivity of 90.12% and a specificity of 91.02% when a cutoff value of 0.46 was used. This diagnostic model showed similar performance in the validation cohort. The area under the curve, sensitivity, and specificity were 0.962, 93.21%, and 90.00%, respectively. Further flow cytometry analysis showed that ESAT-6 stimulation induced a significantly higher mean fluorescence intensity of IFN-γ⁺ cells in lymphocytes compared with culture filtrate protein 10 (CFP-10) stimulation. In contrast, CFP-10 stimulation induced a significantly higher percentage of IFN-γ⁺ cells in lymphocytes compared with ESAT-6 stimulation.

CONCLUSIONS

The combination of the MSS of ESAT-6 SFC and the modified TBAg/PHA ratio of T-SPOT.TB assay showed great value in discriminating ATB from LTBI.

Risk Factors for False-Negative Interferon-γ Release Assay Results in Culture-Confirmed Childhood TB

A negative interferon-γ release assay (IGRA) result might inappropriately lower the clinical suspicion for childhood tuberculosis (TB) and result in delayed treatment initiation. However, the risk factors associated with false-negative IGRA results in children remain unclear. Between May 2012 and January 2018, 156 culture-confirmed childhood TB patients who had received T-SPOT.TB test were included. Data, including demographic information and clinicopathological variables, were collected via questionnaires. Univariate and multivariate logistic regression analyses were performed to estimate the odds ratio (OR) and corresponding 95% CI of risk factors associated with false-negative T-SPOT.TB results. The positive rate of T-SPOT.TB test was 85.9% in childhood TB patients. Multivariate analysis revealed that younger age (≤ 9 years; OR = 4.782; 95% CI: 1.689, 13.539), weight for age (z-score > 0.37; OR = 4.256; 95% CI: 1.458, 12.428), and hypoproteinemia (total protein ≤ 68.4 g/L; OR = 7.131; 95% CI: 1.864, 27.271) were risk factors for false-negative T-SPOT.TB results in childhood TB. Younger age, overweight, and hypoproteinemia were found to be associated with false-negative T-SPOT.TB results in childhood TB. Health care professionals should consider these risk factors when evaluating suspected childhood TB with negative T-SPOT.TB results.

Factors associated with false negative interferon-γ release assay results in patients with tuberculosis: A systematic review with meta-analysis

Which factors are related to false negative results of the interferon-γ release assay (IGRA) is unclear. This systematic review described the risk factors associated with false negative IGRA results. Two authors independently identified studies designed to evaluate risk factors for false negative IGRA results from PubMed, the Cochrane Register of Control Trial database, and EMBASE, accessed on October 22, 2018. Meta-analyses were conducted with random-effect models, and heterogeneity was calculated with the I² method. Of 1,377 titles and abstracts screened, 47 full texts were selected for review, and we finally included 17 studies in this systematic review. The most commonly studied risk factor (14 studies) was advanced age, followed by low peripheral lymphocyte counts (7 studies), and these factors were associated with false negative results even with different tuberculosis incidences (pooled odds ratio 2.06; 95% CI, 1.68–2.52 in advanced age and 2.68; 95% CI, 2.00–3.61 in low peripheral lymphocyte counts). Advanced age and low peripheral lymphocyte counts may be common risk factors for false negative IGRA results, suggesting that people with these factors need to be carefully followed, even if they have negative IGRA results.

Characteristics Associated with Negative Interferon-γ Release Assay Results in Culture-Confirmed Tuberculosis Patients, Texas, USA, 2013-2015

Interferon-γ release assays (IGRAs) are the preferred diagnostic test for tuberculosis (TB) infection in at-risk populations in developed countries. However, IGRAs have high false-negative rates in patients with TB disease. Population-based studies assessing the factors associated with negative IGRA results in TB patients have not been performed. Using statewide TB surveillance data of culture-confirmed TB patients in Texas, USA, during 2013–2015, we describe the patient characteristics and treatment outcomes associated with false-negative IGRA results. Among 2,854 TB patients, 1,527 (53.5%) had an IGRA result; 97.4% (1,487/1,527) of those had a positive (87.7%) or negative (12.3%) result. Older age, HIV co-infection, non-Hispanic white race/ethnicity, and being tested with T-SPOT.TB were associated with negative IGRA results. TB patients with negative IGRA results had a higher mortality, potentially due to delayed treatment. Healthcare providers should consider these risk factors when making decisions for patients with suspected TB and negative IGRA results and potentially provide treatment.

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.

Official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention Clinical Practice Guidelines: Diagnosis of Tuberculosis in Adults and Children

BACKGROUND

Individuals infected with Mycobacterium tuberculosis (Mtb) may develop symptoms and signs of disease (tuberculosis disease) or may have no clinical evidence of disease (latent tuberculosis infection [LTBI]). Tuberculosis disease is a leading cause of infectious disease morbidity and mortality worldwide, yet many questions related to its diagnosis remain.

METHODS

A task force supported by the American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America searched, selected, and synthesized relevant evidence. The evidence was then used as the basis for recommendations about the diagnosis of tuberculosis disease and LTBI in adults and children. The recommendations were formulated, written, and graded using the Grading, Recommendations, Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Twenty-three evidence-based recommendations about diagnostic testing for latent tuberculosis infection, pulmonary tuberculosis, and extrapulmonary tuberculosis are provided. Six of the recommendations are strong, whereas the remaining 17 are conditional.

CONCLUSIONS

These guidelines are not intended to impose a standard of care. They provide the basis for rational decisions in the diagnosis of tuberculosis in the context of the existing evidence. No guidelines can take into account all of the often compelling unique individual clinical circumstances.

Interferon-gamma release assays in patients with Mycobacterium kansasii pulmonary infection: A retrospective survey

OBJECTIVES

Interferon-gamma release assays (IGRAs) can be positive in patients infected with Mycobacterium kansasii (M. kansasii), which carries some of Mycobacterium tuberculosis specific antigens adopted for IGRAs. Our aim is to evaluate positive rate and factors associated with positive IGRAs in patients with M. kansasii pulmonary infection.

METHODS

We retrospectively investigated 105 M. kansasii cases in which IGRAs were performed before or ≦14 days after treatment initiation. Clinical characteristics including a history of tuberculosis, radiographic features and laboratory data were collected from medical records.

RESULTS

Positive rate of each IGRA was 25.9% (15/58) in QuantiFERON TB-Gold (QFT-G), 31.8% (7/22) in QuantiFERON-TB Gold In Tube (QFT-GIT), and 33.3% (7/21) in T-SPOT. TB (T-SPOT). After excluding cases having a history of tuberculosis, positive rate of each IGRA decreased to 19% (8/42) in QFT-G, 20% (3/15) in QFT-GIT, and 18.8% (3/16) in T-SPOT. The multivariate analysis revealed that only previous tuberculosis was significantly associated with positive IGRAs (odds ratio, 4.758; 95% confidence interval, 1.73-13.05; p = 0.002).

CONCLUSIONS

Positive rates of IGRAs were low in patients with M. kansasii, especially in those without previous tuberculosis. M. kansasii pulmonary infection alone might induce less interferon-gamma production with the antigens.

Diagnostic performance of interferon-γ release assay for lymph node tuberculosis

The aim of the study was to evaluate the performance of interferon-γ (IFN-γ) release assay (IGRA) (T-SPOT.TB) for patients with suspected lymph node tuberculosis (TB). Of the 405 patients with suspected lymph node TB, enrolled from Beijing Chest Hospital between July 2011 and April 2015, 83 (20.5%) were microbiologically/histopathologically confirmed lymph node TB, and 282 (69.6%) did not have active TB. The remaining 21 inconclusive TB and 19 clinical TB were excluded from the final analysis (9.9%). T-SPOT.TB using peripheral blood mononuclear cells was performed to examine the IFN-γ response to the Mycobacterium tuberculosis-specific antigens early secretory antigenic target 6 and culture filtrate protein 10. The overall sensitivity and specificity for T-SPOT.TB were 90.4% and 70.5%, respectively. Spot-forming cells in the lymph node TB group (184 [48-596/10(6) peripheral blood mononuclear cells {PBMCs}]) were significantly higher than that in the nonactive TB group (0 [0-41]/10(6) PBMCs) (P<0.001). These results suggest that the IGRA assay could be a useful aid in the diagnosis of lymph node 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.

Interferon release does not add discriminatory value to smear-negative HIV-tuberculosis algorithms

Clinical algorithms for evaluating HIV-infected individuals for tuberculosis (TB) prior to isoniazid preventive therapy (IPT) perform poorly, and interferon-γ release assays (IGRAs) have moderate accuracy for active TB. It is unclear whether, when used as adjunct tests, IGRAs add any clinical discriminatory value for active TB diagnosis in the pre-IPT assessment. 779 sputum smear-negative HIV-infected persons, established on or about to commence combined antiretroviral therapy (ART), were screened for TB prior to IPT. Stepwise multivariable logistic regression was used to develop clinical prediction models. The discriminatory ability was assessed by receiver operator characteristic area under the curve (AUC). QuantiFERON-TB Gold in-tube (QFT-GIT) was evaluated. The prevalence of smear-negative TB by culture was 6.4% (95% CI 4.9-8.4%). Used alone, QFT-GIT and the tuberculin skin test (TST) had comparable performance; the post-test probability of disease based on single negative tests was 3-4%. In a multivariable model, the QFT-GIT test did not improve the ability of a clinical algorithm, which included not taking ART, weight <60 kg, no prior history of TB, any one positive TB symptom/sign (cough ≥ 2 weeks) and CD4+ count <250 cells per mm(3), to discriminate smear-negative culture-positive and -negative TB (72% to 74%; AUC comparison p=0.33). The TST marginally improved the discriminatory ability of the clinical model (to 77%, AUC comparison p=0.04). QFT-GIT does not improve the discriminatory ability of current TB screening clinical algorithms used to evaluate HIV-infected individuals for TB ahead of preventive therapy. Evaluation of new TB diagnostics for clinical relevance should follow a multivariable process that goes beyond test accuracy.

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

OBJECTIVE

The purpose of this study was to examine the usefulness of the TST and the interferon-γ release assays (IGRA) for diagnosing smear-negative pulmonary TB in immunocompromised patients in an intermediate TB burden.

METHODS

We conducted a prospective study enrolling 119 immunocompromised participants with suspected smear-negative pulmonary TB in Seoul, South Korea. Clinical assessment, TST, QuantiFERON-TB Gold In Tube (QFT-GIT), and T-SPOT.TB were performed in immunosuppressed condition.

RESULTS

All participants were categorized according to the type of immunosuppression: 29 patients with diabetes mellitus, 53 with malignancy, 23 with taking immunosuppressive drugs, and 14 with end stage renal disease. IGRA sensitivity and specificity (95% CI) were: QFT-GIT [59.0% (44.9-72.0)] and [61.3% (54.4-67.6)] and T-SPOT.TB [72.0% (54.2-86.2)] and [42.3% (33.8-49.1)], respectively. For TST, sensitivity was 41.2% (28.3-50.8) and specificity was 91.8% (85.8-96.30). The sensitivities of the three diagnostic methods tended to be lower in the immunosuppressive drug group than in other groups (QFT-GIT 11.1%, T-SPOT.TB 40.0% and TST 25.0% in patients with taking immunosuppressive drugs). Among 111 patients who underwent a chest CT examination, there were no significant differences in the CT findings between the immunocompromised TB and non-TB patients.

CONCLUSIONS

The IGRAs and TST had no value as a single test either to rule-in or rule-out active TB in immunocompromised patients in an intermediate burden.

Analysis of factors lowering sensitivity of interferon-γ release assay for tuberculosis

Background

Imperfect sensitivity of interferon-γ release assay (IGRA) is a potential problem to detect tuberculosis. We made a thorough investigation of the factors that can lead to false negativity of IGRA.

Methods

We recruited 543 patients with new smear-positive pulmonary tuberculosis in Hanoi, Viet Nam. At diagnosis, peripheral blood was collected and IGRA (QuantiFERON-TB Gold In-Tube) was performed. Clinical and epidemiological information of the host and pathogen was collected. The test sensitivity was calculated and factors negatively influencing IGRA results were evaluated using a logistic regression model in 504 patients with culture-confirmed pulmonary tuberculosis.

Results

The overall sensitivity of IGRA was 92.3% (95% CI, 89.6%–94.4%). The proportions of IGRA-negative and -indeterminate results were 4.8% (95% CI, 3.1%–7.0%) and 3.0% (95% CI, 1.7%–4.9%). Age increased by year, body mass index <16.0, HIV co-infection and the increased number of HLA-DRB1*0701 allele that patients bear showed significant associations with IGRA negativity (OR = 1.04 [95% CI, 1.01–1.07], 5.42 [1.48–19.79], 6.38 [1.78–22.92] and 5.09 [2.31–11.22], respectively). HIV co-infection and the same HLA allele were also associated with indeterminate results (OR = 99.59 [95% CI, 15.58–625.61] and 4.25 [1.27–14.16]).

Conclusions

Aging, emaciation, HIV co-infection and HLA genotype affected IGRA results. Assessment of these factors might contribute to a better understanding of the assay.

Risk factors for false-negative results of QuantiFERON-TB Gold In-Tube assay in non-HIV-infected patients with culture-confirmed tuberculosis

Limited information is available on the risk factors for false-negative results with the new generation of QuantiFERON-TB Gold In-Tube (QFT-GIT) tests in non-HIV-infected patients with tuberculosis (TB). We sought to identify risk factors for false-negative QFT-GIT results in culture-confirmed TB patients. We reviewed the microbiological, laboratory, radiographic, and clinical data of 362 patients with positive M. tuberculosis cultures who received QFT-GIT tests at a Korean tertiary hospital between September 2006 and March 2010. Of these, 311 (85.9%) had true-positive and 51 (14.1%) had false-negative results. The false-negative group was more likely to have immunosuppressant diseases and lower platelet, protein, and albumin levels than the true-positive group. An immunosuppressive condition was an independent risk factor for false-negative QFT-GIT results in non-HIV-infected patients with active TB (odds ratio, 2.98; 95% confidence interval, 1.38-6.47; P = .006). Careful interpretation of negative QFT-GIT results is thus necessary in immunocompromised patients suspected of having active TB.

[Analysis of patients with positive acid-fast bacilli culture and negative T-SPOT.TB results]

BACKGROUND

T-SPOT.TB is a sensitive test that detects interferon-gamma producing T-cells in tuberculosis patients following stimulation with tuberculosis-specific antigens. Our study was aimed to investigate the possible causes of false negative results of the test by analyzing the patients with positive acid-fast bacilli (AFB) culture and negative T-SPOT.TB results.

METHODS

We investigated 138 patients with positive AFB culture results reported between January 2009 and April 2010. Medical records of these patients were reviewed for the results of T-SPOT.TB test, AFB culture, PCR for Mycobacterium tuberculosis (TB-PCR), chest X-ray, drug treatment, etc. Diagnosis of tuberculosis was confirmed by positive TB-PCR or identification of Mycobacterium tuberculosis (MTB). Sensitivity of T-SPOT.TB test was calculated and the possible causes of AFB culture positive and T-SPOT.TB negative results were analyzed.

RESULTS

T-SPOT.TB test was performed in 63 of the 138 patients with AFB culture positive results. Fifty-six (88.9%) were positive and 7 patients (11.1%) were negative on T-SPOT.TB test. Of these 7 negative cases, 4 were confirmed as nontuberculous mycobacteria (NTM), 2 were suspected as NTM and diagnosis could not be confirmed in 1. Six of these 7 patients were over 70 yr old and 6 patients had lymphocytopenia. T-SPOT.TB negative results were not observed in any of the 44 patients confirmed to have active tuberculosis (sensitivity 100%).

CONCLUSIONS

Our results suggest that T-SPOT.TB test is very sensitive for diagnosing active tuberculosis. NTM may be the main cause of AFB culture positive and T-SPOT.TB negative results, but MTB infection in immunocompromised patients also has to be considered.