Clinical Reevaluation of the QuantiFERON TB-2G Test as a Diagnostic Method for Differentiating Active Tuberculosis from Nontuberculous Mycobacteriosis

Accuracy of QuantiFERON in active tuberculosis suspects with comorbidities and nontuberculous mycobacterial infection in Northern California

The QuantiFERON-TB Gold (QFT) is routinely utilized in North American health systems to detect a cellular immune response to Mycobacterium tuberculosis antigens in symptomatic and asymptomatic patients. The sensitivity of QFT in tuberculosis (TB) patients with comorbidities is not well established and the specificity of QFT in patients with nontuberculous mycobacteria (NTM) infections is incompletely understood. Between 2012 and 2023, all patients with culture-positive TB and patients with NTM infection per the expert diagnostic guidelines or biopsy-proven NTM infection who had a concurrent QFT test were included in this study. The sensitivity and specificity of QFT were measured in TB and NTM patients, respectively. In 109 patients with active TB, the overall sensitivity of QFT was 78.0% (85/109; 95% CI: 70.1, 85.7). The sensitivity was 86.0% (49/57; 95% CI: 76.6, 94.8) and 69.2% (36/52; 95% CI: 56.7, 81.8) in immunocompetent and immunocompromised patients, respectively. The overall specificity of QFT in 88 patients with NTM infection was 76.1% (67/88; 95% CI: 67.2, 85.0). After the exclusion of 17 NTM patients with risk factors for latent TB infection, the specificity was 94.4% (67/71; 95% CI: 89.1, 99.7). Two patients had NTM species known to cross-react with QFT. In two NTM patients infected with species (Mycobacterium intracellulare subsp. intracellulare and Mycobacterium intracellulare subsp. chimaera) not known to cross-react, whole genome sequencing did not detect ESAT-6 or CFP-10. In Northern California, the QFT assay demonstrated moderately low to moderately high sensitivity in TB patients and very high specificity in NTM patients, thus ruling out concerns for cross-reactivity with NTM.

Haemorrhagic Mycobacterium avium complex pericarditis presenting with cardiac tamponade in an immunocompetent woman

A young woman in her mid-40s was referred by her primary care physician for fever, worsening shortness of breath, pleuritic chest pain and tachycardia. CT angiogram of the chest revealed a large pericardial effusion. Echocardiogram confirmed tamponade physiology despite her being haemodynamically stable. She had an emergency pericardiocentesis which revealed evidence of a haemorrhagic pericardial effusion. However, the patient was still symptomatic after treatment and had to undergo video-assisted thoracoscopic surgery with a pericardial window and chest tube. Postoperatively, her fevers resolved. Pan-culture was initially negative, and all antibiotics were discontinued. Acid-fast bacilli cultures later grew Mycobacterium avium complex. She continued to have chest discomfort postoperatively, but follow-up CT of the chest 3 months postoperatively showed continued resolution of her pericardial effusion. The patient's symptoms improved, and she has had no recurrence of effusion without the need for anti-tuberculosis drugs.

Performance of Interferon-γ Release Assays in Patients with Mycobacterium kansasii Infection

Objective

To evaluate the performance of interferon-γ release assays (IGRAs) in patients with Mycobacterium kansasii infection.

Methods

Consecutive patients between May 2012 and June 2021 who had positive for mycobacterial cultures and who underwent IGRAs (T-SPOT.TB or QuantiFERON-TB Gold [QFT-G]) were included in the analysis. The IGRA positivity rates among patients with M. kansasii isolates were then calculated. If M. kansasii was identified in at least two sputum samples or in sterile samples, M. kansasii disease was then diagnosed. Otherwise, colonisation was considered.

Results

During the study period, 54 patients with M. kansasii infection underwent T-SPOT.TB (n=48) or QFT-G (n=6) assays. The mean age was 44.1±13.4 years, 85.2% (46/54) were male. Eight patients were diagnosed with M. kansasii disease and another 46 patients were considered to have colonisation. Twenty-four patients (T-SPOT.TB, n=23; QFT-G, n=1) were positive for IGRAs, for an overall rate of 44.4% (24/54; T-SPOT.TB, 47.9% [23/48]; QFT-G, 16.7% [1/6]) for IGRAs, 25.0% (2/8) for M. kansasii disease, and 47.8% (22/46) for colonisation.

Conclusion

Positive IGRA rates were relatively low in patients with M. kansasii infection. More efforts are required to improve the performance of IGRAs in diagnosing M. kansasii infection.

Evaluation of role of interferon gamma release assays in the diagnosis of latent tuberculosis in human immunodeficiency virus-infected patients

Introduction:

Tuberculosis (TB) is the most common opportunistic infection in human immunodeficiency virus (HIV)-infected individuals. The risk of eventually developing active TB from latent TB infection (LTBI) is about 10% per year in HIV-positive patients in contrast to 10% lifetime risk in HIV-negative patients. Until recently, the tuberculin skin test (TST) was the only tool available for diagnosing LTBI. Interferon-gamma release assays (IGRAs) were recently developed and address many of the limitations of TST test, especially in immunocompromised state.

Aims and Objectives:

(1) To determine the prevalence of latent, active pulmonary, and multidrug-resistant (MDR)-TB among HIV-positive patients in and around Aligarh region; (2) sensitivity and specificity of TST and IGRAs for diagnosis of LTBI in HIV positive patients; and (3) to assess drug resistance and mutational patterns of the clinical isolates of MDR-TB in HIV-TB co-infection.

Materials and Methods:

A cross-sectional study was done on all the patients attended the ICTC centre, JNMC, AMU Aligarh, seropositive for HIV, i.e. 469 (sample size) for the study period of 2 years from October 2015 to October 2017. All 469 HIV-positive patients were screened for latent and active pulmonary TB. Diagnosis of TB (active and latent) was made using clinical, radiological, and microbiological tests. TST and IGRA testing along with CD4 cell counts were also determined. Line probe assay was also done to assess drug resistance and mutational patterns of MDR-TB in HIV patients.

Results:

In our study, prevalence of HIV infection was 5.04%. Sixty-seven (14.28%) patients were as active TB (HIV-TB co-infection), out of which only one patient (1.49%) was confirmed as MDR-TB, 117 (24.94%) were diagnosed as LTBI. It was also evaluated that IGRA has more sensitivity (75%) and specificity (76%) than TST with sensitivity of 71.7% and specificity 66%.

Conclusion:

As there is no gold standard test for latent TB, longitudinal follow-up is needed to interpret discordant test results. There is a need to interpret negative QFT results with caution and to test for latent TB at higher CD4 counts, if possible. Interferon gamma assays can become better tool for diagnosis of especially for latent TB. However, more research study required for establish their relevance, especially in immunocompromised states.

Diagnosis of Mycobacterium marinum Infection Based on Seroconversion of QuantiFERON-TB Gold Test

Mycobacterium marinum is a slow-growing photochromatic acid fast bacilli (AFB). Following exposure of injured skin to fish tanks and other aquatic bodies, it usually causes indolent skin and soft tissue infections. Incubation period differs but it is generally long; hence, diagnosis is often missed leading to delay in treatment. Obtaining proper history along with histopathology and cultures leads to diagnosis. There is evidence of cross-reactivity of M. marinum with QuantiFERON-TB gold test. In patients without risk factors for tuberculosis, recent seroconversion may provide a clue to diagnosis and eliminate differentials. We present a case of M. marinum skin and soft tissue infection diagnosed based on seroconversion of QuantiFERON-TB gold test in an immunocompromised patient. This was confirmed by AFB culture after six weeks.

A Case Report of Peritoneal Tuberculosis: A Challenging Diagnosis

Peritoneal tuberculosis is a disease which can mimick malignancy especially in women who present with ascites and elevated CA125 levels. It should always be considered in differential diagnosis, but the diagnosis is rarely easy for clinicians. A young female patient who presented with abdomen tenderness and diagnosed with peritoneal tuberculosis as a result of performed tests is discussed hereby in the case report. We expect that this case report adds to the existing literature on this subject.

Usefulness of interferon-γ release assay for the diagnosis of sputum smear-negative pulmonary and extra-pulmonary TB in Zhejiang Province, China

Background

Quick diagnosis of smear-negative pulmonary tuberculosis (TB) and extra-pulmonary TB are urgently needed in clinical diagnosis. Our research aims to investigate the usefulness of the interferon-γ release assay (IGRA) for the diagnosis of smear-negative pulmonary and extra-pulmonary TB.

Methods

We performed TB antibody and TB-IGRA tests on 389 pulmonary TB patients (including 120 smear-positive pulmonary TB patients and 269 smear-negative pulmonary TB patients), 113 extra-pulmonary TB patients, 81 patients with other pulmonary diseases and 100 healthy controls. Blood samples for the TB-Ab test and the TB-IGRA were collected, processed, and interpreted according to the manufacturer’s protocol.

Results

The detection ratio of smear-positive pulmonary TB patients and smear-negative pulmonary TB patients were 90.8% (109 of 120) and 89.6% (241 of 269), respectively. There was no statistically significant difference of its performance between these two sample sets (P > 0.05). The detection ratio of positive TB patients and extra-pulmonary TB patients were 90.0% (350 of 389) and 87.6% (99 of 113), respectively, which was not significantly different (P > 0.05).

Conclusions

In this work, the total detection ratio using TB-IGRA was 89.4%, therefore TB-IGRA has diagnostic values in smear-negative pulmonary TB and extra-pulmonary TB diagnosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0331-1) contains supplementary material, which is available to authorized users.

Assessment of the QuantiFERON-TB Gold In-Tube test for the detection of Mycobacterium tuberculosis infection in United States Navy recruits

Background

Immunologic tests such as the tuberculin skin test (TST) and QuantiFERON^®-TB Gold In-Tube test (QFT-GIT) are designed to detect Mycobacterium tuberculosis infection, both latent M. tuberculosis infection (LTBI) and infection manifesting as active tuberculosis disease (TB). These tests need high specificity to minimize unnecessary treatment and high sensitivity to allow maximum detection and prevention of TB.

Methods

Estimate QFT-GIT specificity, compare QFT-GIT and TST results, and assess factor associations with test discordance among U.S. Navy recruits.

Results

Among 792 subjects with completed TST and QFT-GIT, 42(5.3%) had TST indurations ≥10mm, 23(2.9%) had indurations ≥15mm, 14(1.8%) had positive QFT-GIT results, and 5(0.6%) had indeterminate QFT-GITs. Of 787 subjects with completed TST and determinate QFT-GIT, 510(64.8%) were at low-risk for infection, 277(35.2%) were at increased risk, and none had TB. Among 510 subjects at low-risk (presumed not infected), estimated TST specificity using a 15mm cutoff, 99.0% (95%CI: 98.2–99.9%), and QFT-GIT specificity, 98.8% (95%CI: 97.9–99.8%), were not significantly different (p>0.99). Most discordance was among recruits at increased risk of infection, and most was TST-positive but QFT-GIT-negative discordance. Of 18 recruits with TST ≥15mm but QFT-GIT negative discordance, 14(78%) were at increased risk. TB prevalence in country of birth was the strongest predictor of positive TST results, positive QFT-GIT results, and TST-positive but QFT-GIT-negative discordance. Reactivity to M. avium purified protein derivative (PPD) was associated with positive TST results and with TST-positive but QFT-GIT-negative discordance using a 10 mm cutoff, but not using a 15 mm cutoff or with QFT-GIT results.

Conclusions

M. tuberculosis infection prevalence was low, with the vast majority of infection occurring in recruits with recognizable risks. QFT-GIT and TST specificities were high and not significantly different. Negative QFT-GIT results among subjects with TST induration ≥15 mm who were born in countries with high TB prevalence, raise concerns.

Use of the QuantiFERON-TB Gold In-Tube Test in the Diagnosis and Monitoring of Treatment Efficacy in Active Pulmonary Tuberculosis

The value of QuantiFERON in the diagnosis of tuberculosis disease and in the monitoring of the response to anti-tuberculosis treatment is unclear. The aims of this study were to evaluate the accuracy of the QuantiFERON-TB Gold In-Tube (QFT-GIT) test in the diagnosis of tuberculosis and in the monitoring of the response to anti-tuberculosis treatment in patients with active pulmonary tuberculosis (PTB). Between January 2013 and December 2015, 133 cases with active PTB and 133 controls with no mycobacterial infection, matched by age (within 3 years) and by the week that they visited Tainan Chest Hospital, were enrolled in the study. Serial testing by QFT-GIT at baseline and after 2 and 6 months of treatment was performed. At these time points, a comparison of the performance of QFT-GIT with that of sputum culture status among study subjects was conducted. Compared to baseline, 116 (87.2%) cases showed a decreased response, whereas 17 (12.8%) showed persistent or stronger interferon-gamma (IFN-γ) responses at 2 months. PTB patients IFN-γ responses declined significantly from baseline to 2 months (median, 6.32 vs. 4.12; p < 0.005). The sensitivity values of the QFT-GIT test for the detection of pulmonary tuberculosis at cut-off points of 0.35 IU/mL, 0.20 IU/mL, and 0.10 IU/mL were 74.4%, 78.2%, and 80.5%, respectively. The specificity values at cut-off points of 0.35 IU/mL, 0.20 IU/mL, and 0.10 IU/mL were 66.2%, 63.9%, and 57.1%, respectively. Our results support the QFT-GIT assay as a potential tool for diagnosing tuberculosis and for monitoring the efficacy of anti-tuberculosis treatment.

The performance of interferon-gamma release assay in nontuberculous mycobacterial diseases: a retrospective study in China

Background

The interferon-gamma release assay (IGRA) is more specific than the tuberculin skin test to discriminate between tuberculosis (TB) and nontuberculous mycobacterial (NTM) diseases. Here we performed a retrospective study to evaluate the performance of the T-SPOT.TB in patients with NTM diseases.

Methods

Between March, 2013 and Nov, 2015, a total of 58 patients with NTM diseases had a T-SPOT.TB performed were enrolled, 30 patients had definite NTM diseases, 28 had probable diseases. Their clinicopathological characteristics were reviewed and analyzed. Cultures for mycobacteria were performed. The indirect proportion method with Löwenstein–Jensen (L-J) medium was used for first-line drug susceptibility test. T-SPOT.TB assay was performed according to the manufacturer’s instructions. Data were expressed as mean ± standard deviation (continuous variables) and as numbers and percentages (categorical variables). The χ² test was used for comparisons between proportions.

Results

The average age was 51.8 ± 16.1 years (range 10 to 77 years), 58.6% (34/58) were male. 16.4% (9/55) were TB-PCR positive. 34 (58.6%) isolates were Mycobacterium intracellulare, ten (17.2%) were Mycobacterium chelonae and seven (12.1%) were Mycobacterium fortuitum. Fifty-two (89.7%) patients were NTM lung disease, five (8.6%) were pleural disease, and one (1.7%) lymphadenitis. The total positivity of T-SPOT.TB was 53.4% (31/58) among the whole group (probable and definite). For probable cases, the T-SPOT.TB assay was positive in 53.5% (15/28); for definite cases, 16 (53.3%) of 30 definite cases were positive. There was no statistical difference in the positivity rate between them (P < 0.01).

Conclusions

In the study, we showed that a significant portion of NTM diseases were T-SPOT.TB positive in China. Although T-SPOT.TB is useful diagnostic method for differentiating TB from NTM diseases, in China, the IGRA assay show limited value in the discrimination. In addition, further research is needed to investigate the association between TB infection and treatment for NTM patients.

Mycobacterium avium Auricular Infection in an Apparent Immunocompetent Patient: A Case Report

INTRODUCTION

Soft tissue infections with Mycobacterium avium complex are more likely to appear in immunocompromised patients. However, they may rarely arise in non-immunosuppressed individuals.

AIM

To present the case of an ear infection with Mycobacterium avium in the absence of demonstrable immunosuppression.

CASE REPORT

Clinical case description, blood tests, routine histology and tissue cultures.

DISCUSSION

A female, apparent immunocompetent patient presented with a 6-month reddish, oedematous and painless lesion with fine scaling in the right ear. Histology showed numerous granulomas, composed of epithelioid histiocytes without central necrosis. Cultures grew Mycobacterium avium. An unusual accidental ear injury was the portal of microbial entry. The patient's lesion fully regressed after a 9-month course of antibiotics.

CONCLUSION

Although M. avium infections are rare in immunocompetent patients, the possibility of such infections should be considered even in these subjects, when relevant clinical features and exposure to risk factors are present.

Usefulness of two interferon-γ release assays for rheumatic disease

BACKGROUND

The aim of this study was to evaluate the performance of two interferon-γ release assays (IGRA), QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB, for pediatric patients with rheumatic disease in Japan and to analyze the frequencies of indeterminate test results with these kits.

METHODS

An IGRA was performed in 108 patients <20 years old in order to exclude tuberculosis infection at the time of first application of or change of biological agents and immunosuppressants in Yokohama City University Hospital.

RESULTS

None of the 108 patients tested had active tuberculosis during the 50 month observation period. Indeterminate results of QFT-GIT and T-SPOT.TB tests were obtained in 9.9% and in 0% of cases, respectively. Indeterminate results were obtained significantly more frequently in patients on prednisolone >0.5 mg/kg and in patients with active underlying disease. Use of biologicals and other immunosuppressants had no effect on these measurements.

CONCLUSIONS

IGRA are very useful for excluding tuberculosis infection in patients with rheumatic disease before starting new immunosuppressant therapy. Furthermore, the T-SPOT.TB test was suitable for evaluating latent tuberculosis infection even under immunosuppression, when TB tests are generally hard to perform.

Non-tuberculous mycobacteria and the performance of interferon gamma release assays in Denmark

BACKGROUND

The QuantiFERON-TB-Gold Test (QFT) is more specific than the Mantoux skin-test to discriminate between Mycobacterium tuberculosis (MTB) and non-tuberculous mycobacterial (NTM) infections. Here we study the performance of the QFT in patients with NTM disease.

METHODS

From 2005 to 2011, nationwide patient data on positive NTM cultures (n = 925) were combined with nationwide data on QFT results (n = 16,133), both retrieved from the International Reference Laboratory of Mycobacteriology, Denmark. A total of 112 patients with NTM infections had a QFT performed, 53 patients had definite NTM disease, 10 had possible disease and 49 had NTM colonization.

RESULTS

QFT was positive in 8% (4/53) of patients with definite disease, 40% (4/10) with possible disease and 31% (15/49) with colonization. Positivity rate was lowest among patients with definite disease infected with NTM without the RD1 region 4% (2/50). None of the 15 children with MAC lymphadenitis had a positive QFT.

CONCLUSION

This study is one of the largest assessing IGRAs in patients with NTM disease in a TB low-incidence setting. Our study showed that the QFT holds potential to discriminate between NTM and MTB infections. We found no positive IGRA test results among children with NTM not sharing the RD1-region of MTB resulting in a 100% specificity and we suggest that a QFT in a child presenting with cervical lymphadenitis may be helpful in distinguishing NTM from TB lymphadenitis.

Management of nontuberculous mycobacterial infection in the elderly

The incidence of nontuberculous mycobacteria (NTM) has increased over the last decades. Elderly people are more susceptible to NTM and experience increased morbidities. NTM incidence is expected to rise due to an increasing elderly population at least up to 2050. Given the importance of NTM infection in the elderly, an increasing interest exists in studying NTM characteristics in the aged population. In this review, we summarize the characteristics of NTM infection among elderly patients. We focus on epidemiology, clinical presentation, and treatment options of NTM in this age group. We highlight the differences in the diagnosis and treatment between rapid and slow growing mycobacterial infections. The current recommendation for treatment of NTM is discussed. We debate if in vitro susceptibility testing has a role in the treatment of NTM. Drug-drug interaction between antibiotics used to treat NTM and other medications, particularly warfarin, is another important issue that we discuss. Finally, we review the prognosis of NTM disease in elderly patients.

Whole blood assay and visceral leishmaniasis: Challenges and promises

For years, the ability to study immune responses in patients with active visceral leishmaniasis (VL) has been hampered by the absence of detectable antigen-specific Th1 responses using cells from peripheral blood mononuclear cells (PBMCs). Employing whole blood assay (WBA), we recently reported that whole blood cells of active VL patients maintain the capacity to secrete significant levels of antigen driven IFN-γ and IL-10. Furthermore, WBA that uses soluble leishmania antigen (SLA) have advantages over the leishmanin skin test (LST), in terms of higher specificity and better correlation with surrogate markers of exposures to Leishmania donovani. These findings open the door to a series of immunological and epidemiological studies not previously possible for VL. In the present review, we discuss current status, future perspectives as well as obstacles in the research on WBA. Research in this area is essential for development of potential immunological and epidemiological tools for VL.

Pulmonary disease caused by nontuberculous mycobacteria

The propensity of various nontuberculous mycobacteria to cause lung disease varies widely and is conditioned by host factors; infection is believed to occur from environmental sources. Nontuberculous mycobacteria pulmonary disease (PNTM) is increasing worldwide and Mycobacterium avium complex is the most common cause. PNTM usually occurs in one of three prototypical forms: hypersensitivity pneumonitis, cavitary tuberculosis-like disease or nodular bronchiectasis. PNTM has been linked in some patients to genetic variants of the cystic fibrosis transmembrane conductance regulator gene and a distinct patient phenotype. Interactions between PNTM and other comorbidities are also increasingly appreciated. Guidelines for diagnosis, emphasizing chest imaging and microbiology, have been published; speciation using molecular techniques is critical for accuracy and for treatment decisions. Clinical trials are lacking to inform treatment for many species and experience with M. avium complex and several others species serves as a guide instead. Use of multiple drugs for a period of at least 12 months following sputum conversion is the norm for most species. In vitro drug susceptibility results for many drugs may not correlate with clinical outcomes and such testing should be done on a selective basis.

Intracranial tuberculoma in non-immunosuppressive state

The rise in the incidence of tuberculosis is generally related to human immunodeficiency virus infection. However, intracranial tuberculoma, a complication of tuberculosis considered to be a critical disease, can develop even in the absence of immunosuppressive state. Here, we describe 2 cases of intracranial tuberculoma occurring in patients with no evidence of immunosuppressive state or past history of tuberculosis. In Case 1, lesions were observed in the right lateral ventricle, with histological examination revealing granulomatous lesions. In Case 2, scattered lesions were observed in the cranium and the lung fields. In both cases, the QuantiFERON Test (QFT) was positive, and improvements were observed in the symptoms following administration of antituberculous drugs. Intracranial tuberculoma cannot be considered rare, and needs to be included in the differential diagnosis of intracranial lesions. Diagnosis can be tricky since this disease can develop in a patient in a non-immunosuppressive state or without a past history of tuberculosis. The QFT is an effective test to enable the diagnosis of tuberculomas in atypical patients.

Comparison of quantiferon test with tuberculin skin test for the detection of tuberculosis infection in children

The efficacy of Quantiferon-TB gold test (QFT-GIT) remains to be documented in pediatric population. Tuberculin skin test (TST) is a conventional test available for the diagnosis of latent tuberculosis infection (LTBI). We aimed to investigate the concordance between QFT-GIT and TST in children with and without tuberculosis infection. Ninety-seven patients, aged 3 months–14 years, admitted to pediatric outpatient clinics of Dr. Sadi Konuk Training Hospital Bakırköy, Turkey between March 2008 and April 2009 were recruited. Demographic features, TST results, history of exposure to active tuberculosis (TB), chest X-ray findings, clinical history, presence of Bacillus Calmette Guerin (BCG) vaccination scar were recorded. Patients were categorized into four groups namely, active TB, LTBI, no TB and healthy. It was found that BCG scar positivity did not influence QFT-GIT results. There was a statistically significant agreement between QFT-GIT and TST results (κ = 0.486; p < 0.01). In patients ≥5 years of age, TST positivity and QFT positivity had a significant relationship (p < 0.01). In all patient groups, sensitivity and specificity was 65.85 % and 82.14 %, respectively. In active TB group, TST and QFT-GIT results demonstrated significant agreement ratio of 40.8 % (κ = 0.364; p < 0.01). Sensitivity and specificity was 100 % and 30 %, respectively. Utilization of QFT-GIT in the diagnosis of LTBI reduces false-positive results and prevents unnecessary treatment with INH and its adverse effects.

QuantiFERON-TB Gold In-Tube test for diagnosis of latent tuberculosis (TB) infection in solid organ transplant candidates: a single-center study in an area endemic for TB

BACKGROUND

The prevalence of Mycobacterium tuberculosis in transplant recipients is estimated to be 50 times higher than in the general population, with a mortality rate of around 40%. Diagnosis and treatment of latent tuberculosis (TB) infection (LTBI) is an essential strategy for TB control. In this study we compared the QuantiFERON-TB Gold In-Tube test (QFT) with the tuberculin skin test (TST) for detection of LTBI in solid organ transplant (SOT) candidates.

PATIENTS AND METHODS

Between March 2008 and September 2011, 187 transplant candidates, who were referred to the transplant clinic of Imam-Khomeini Hospital, were enrolled in the study. Patients were screened for LTBI with both QFT and TST. Twenty-three patients (12.3%) were excluded for failure to follow up. Concordance between the 2 tests, and variables associated with test discordance were assessed.

RESULTS

The mean age of patients was 40 years (range: 11-65) and male-to-female ratio was 1.2 (88/76). TST and QFT were positive in 26 (15.9%) and 33 (20.1%) patients, respectively. Five cases (3.1%) had indeterminate QFT. Overall agreement between QFT and TST was about 80% (k = 0.32, P-value = 0.0001).

CONCLUSION

Considering the fair overall agreement between the 2 tests, and greater ease of the QFT from the patient's point of view, QFT is recommended for detection of LTBI in SOT candidates.

Distinct clinical features in nontuberculous mycobacterial disease with or without latent tuberculosis infection

Nontuberculous mycobacteria (NTM) diseases are in the face of a progressive increase even in immune-competent subjects, and the clinical features of NTM diseases are heterogenous. The decision to institute treatment of the patients should be made after a period of follow up, because therapy is often prolonged, and frequently ineffective. The reasons why some patients develop severe NTM diseases are not clear. Here we observed the involvement of latent tuberculosis infection (LTBI) in clinical and laboratory features of NTM diseases. We evaluated various tuberculosis-related inflammatory markers including osteopontin (OPN), pentraxin-3 (PTX-3), and soluble IL-2 receptor (sIL-2R) in NTM infected patients with or without LTBI. Eight NTM and 5 tuberculosis (TB) patients, and 5 healthy subjects were enrolled. Polymerase Chain Reaction (PCR) analysis confirmed the absence of tuberculosis specific gene (RD1 region), among clinical isolates from NTM patients. Interferon-γ (IFN-γ) release assay (IGRA) using Early Secreted Antigenic Target-6 (ESAT-6) and CFP-10, the RD1-encoded protein, was employed for determining LTBI. IGRA was positive in 4/8 NTM (NTM with LTBI, 50%) and 5/5 TB patients. Only 2 of 4 NTM with LTBI were under chemotherapy among all NTM patients, and others were followed up. The plasma levels of OPN, PTX3 and sIL-2R were significantly higher in NTM patients with LTBI than in those without LTBI (P < 0.05). The two patients under therapy showed the highest OPN levels that persisted after treatment. The increased inflammatory levels in NTM patients with LTBI indicate enhanced inflammatory reaction. Extensive therapy may be necessary in such patients.

Serial interferon-gamma release assays for the diagnosis of latent tuberculosis infection in patients treated with immunosuppressive agents

Background

We assessed the efficacy of serial interferon-gamma release assays (IGRAs) for the diagnosis of latent tuberculosis infection (LTBI) in patients receiving immunosuppressive agents for treatment of rheumatic diseases in Korea.

Methods

Of 276 patients who underwent consecutive screening with one of two IGRAs [QuantiFERON-TB Gold or QuantiFERON-TB Gold In-Tube], 66 patients were evaluated by the serial IGRA for detection of LTBI during therapy with immunosuppressive agents. Information on clinical diagnosis, medication, previous TB, blood cell count, tuberculin skin test, and interferon-gamma (IFN-γ) level measured by IGRA was collected.

Results

Of the 66 patients, the initial IGRA was positive in 24.2%, negative in 65.2%, and indeterminate in 10.6%. Forty-six patients (69.7%) showed consistent IGRA results during follow-up, and 13 patients (19.7%) had consistently positive results. IGRA conversion rate was 12.1% (8/66) and reversion rate was 4.5% (3/66). Conversion of IGRA results was only observed in ankylosing spondylitis patients, and the median interval between the two tests in patients with conversion was 8.5 months. The mean IFN-γ level in the group of patients with consistently positive IGRA results was higher than that in the group with inconsistently positive results, although this trend was not statistically significant (P=0.293). Indeterminate results were observed most frequently in patients with systemic lupus erythematosus.

Conclusions

In patients receiving immunosuppressive agents, both IGRA conversions and reversions were observed. Serial IGRA testing may not be needed in patients with a positive initial IGRA result showing high IFN-γ levels, because of high consistency in the test results.

Diagnosis of latent tuberculosis: Can we do better?

Latent tuberculosis infection (LTBI) is often diagnosed by the tuberculin skin test (TST). The latter has several limitations with regard to its sensitivity and specificity. It may be positive in people with prior bacille Calmette-Guérin (BCG) vaccination or exposure to nontuberculous mycobacteria. False negative TST results frequently occur in patients with impaired T-cell function. Therefore TST results have to be interpreted taking into consideration the pretest risk of TB infection or reactivation. Recently, interferon gamma release assays (IGRA) were introduced for the diagnosis of LTBI. These include the T-SPOT-TB and the QuantiFERON^®-TB Gold tests.These tests measure interferon gamma released in response to T-cell stimulation by specific Mycobacterium tuberculosis antigens. These tests have been shown to be more specific than the TST as they are not affected by BCG vaccination. Their sensitivity was similar to that of the TST and in some studies they correlated better with the degree of exposure. In immune-compromised patients their sensitivity was better than that of the TST. IGRA tests were shown to have better predictive value for the development of active disease among individuals with LTBI. These tests are expensive. Their most cost-effective utilization is as confirmatory tests in patients with positive TST results, particularly in areas with high rates of BCG vaccination.

[Prevalence of latent tuberculosis infection among health care workers from the emergency department of Meaux hospital using an interferon gamma release assay]

OBJECTIVE

To determine the prevalence of the latent tuberculosis infection (LTBI) among health care workers (HCW) of the emergency ward of Meaux hospital, by comparing it with two witnesses units: the orthopaedic surgery ward (referral service to low risk) and the respiratory ward (referral service to high risk).

METHODS

From July to December 2008, on a voluntary basis, anonymised blood samples of any HCW of the three departments were carried out by the occupational health service. Determination of interferon gamma was released by the test "QuantiFERON-TB Gold" (QFT).

RESULTS

Of the 137 eligible subject sampled, 16 had a positive QFT test: nine in the emergency ward, six in the respiratory ward and one in the orthopaedic surgery ward. The proportion of HCW with a positive QFT test was not significantly different between the three wards.

DISCUSSION

This study shows that HCWs of the emergency ward of the Meaux hospital are not working in a department where the risk of LTBI is high.

CONCLUSION

Our study shows that, in a territory of health where the incidence of the tuberculosis disease is superior to the national average, the emergency department of Meaux hospital does not belong to an area at high risk of LTBI. It underlines the interest of QFT test for the screening of LTBI among vaccinated persons.

QuantiFERON TB gold testing for tuberculosis screening in an inflammatory bowel disease cohort in the United States

BACKGROUND

Reactivation of latent Mycobacterium tuberculosis (TB) is a rare, yet devastating infectious complication associated with anti-tumor necrosis factor alpha (TNF-α) therapy. We evaluated the performance of the QuantiFERON TB Gold test (QFT-G) for TB screening in a cohort of inflammatory bowel disease (IBD) patients in the United States.

METHODS

We performed a retrospective, observational study of patients initiated and/or maintained on an anti-TNF-α agent in a single IBD referral center and recorded the frequency and the test results of QFT-G testing and the rate of TB reactivation.

RESULTS

512 QFT-G tests were done in 340 patients. Five patients (1.5%) had a positive, nine (2.7%) indeterminate, and 326 patients (95.8%) had a negative QFT-G. After a mean follow-up of 17 months there was one case of TB reactivation (0.3%). The use of immunosuppressive therapy or anti-TNF therapy at the time of testing did not affect the results of the QFT-G testing. Test-retest had substantial concordance (κ = 0.72). 25% of patients (n = 85) had TST testing. Concordance between the TST and QFT-G was found to be moderate (κ = 0.4152, P = 0.0041).

CONCLUSIONS

Most patients with negative QFT-G tolerated anti-TNF therapy with no evidence of TB reactivation. Concomitant use of immunosuppressive therapy or anti-TNF did not seem to affect QFT-G results. One patient had an indeterminate QFT-G while on infliximab and later developed miliary TB. Concordance with TST is moderate.

Serial interferon-gamma release assays during treatment of active tuberculosis in young adults

Background

The role of interferon-γ release assay (IGRA) in monitoring responses to anti-tuberculosis (TB) treatment is not clear. We evaluated the results of the QuantiFERON-TB Gold In-tube (QFT-GIT) assay over time during the anti-TB treatment of adults with no underlying disease.

Methods

We enrolled soldiers who were newly diagnosed with active TB and admitted to the central referral military hospital in South Korea between May 1, 2008 and September 30, 2009. For each participant, we preformed QFT-GIT assay before treatment (baseline) and at 1, 3, and 6 months after initiating anti-TB medication.

Results

Of 67 eligible patients, 59 (88.1%) completed the study protocol. All participants were males who were human immunodeficiency virus (HIV)-negative and had no chronic diseases. Their median age was 21 years (range, 20-48). Initially, 57 (96.6%) patients had positive QFT-GIT results, and 53 (89.8%), 42 (71.2%), and 39 (66.1%) had positive QFT-GIT results at 1, 3, and 6 months, respectively. The IFN-γ level at baseline was 5.31 ± 5.34 IU/ml, and the levels at 1, 3, and 6 months were 3.95 ± 4.30, 1.82 ± 2.14, and 1.50 ± 2.12 IU/ml, respectively. All patients had clinical and radiologic improvements after treatment and were cured. A lower IFN-γ level, C-reactive protein ≥ 3 mg/dl, and the presence of fever (≥ 38.3°C) at diagnosis were associated with negative reversion of the QFT-GIT assay.

Conclusion

Although the IFN-γ level measured by QFT-GIT assay decreased after successful anti-TB treatment in most participants, less than half of them exhibited QFT-GIT reversion. Thus, the reversion to negativity of the QFT-GIT assay may not be a good surrogate for treatment response in otherwise healthy young patients with TB.

Clinical utility of the QuantiFERON-TB Gold In-Tube test for the diagnosis of active pulmonary tuberculosis

We evaluated the usefulness of interferon-gamma release assays (IGRAs) in the diagnosis of active tuberculosis (TB) in routine clinical practice. We retrospectively assessed the diagnostic usefulness of the QuantiFERON-TB Gold In-Tube (QFT-IT) test in 519 consecutive patients who were suspected of having active pulmonary TB and had QFT-IT test results. Active pulmonary TB was diagnosed in 242 patients (47%). The sensitivity in the diagnosis of active pulmonary TB was higher with the QFT-IT test (84%) than with the tuberculin skin test (TST; 74%; p=0.003). The negative predictive value in the diagnosis of active pulmonary TB was also higher with the QFT-IT test (79%) than with the TST (70%; p=0.023). Among 59 patients with non-tuberculous mycobacterial lung disease, the QFT-IT test was positive in 29 patients (49%). In conclusion, the high negative predictive value of the QFT-IT suggests a supplementary role for this test in the diagnostic exclusion of active TB. However, negative QFT-IT test results should not be used alone to exclude active TB. Additionally, the QFT-IT test has limited usefulness in differentiating active pulmonary TB from non-tuberculous mycobacterial lung disease in areas with a high prevalence of latent tuberculosis infection.

Evidence-based comparison of commercial interferon-gamma release assays for detecting active TB: a metaanalysis

Test accuracy of interferon-gamma release assays (IGRAs) for diagnosing TB differs when using older or precommercial tools and inconsistent diagnostic criteria. This metaanalysis critically appraises studies investigating sensitivity and specificity of the commercial T-Spot.TB and the QuantiFERON-TB Gold In-Tube Assay (QFT-IT) among definitely confirmed TB cases. We searched Medline, EMBASE, and Cochrane bibliographies of relevant articles. Sensitivities, specificities, and indeterminate rates were pooled using a fixed effect model. Sensitivity of the tuberculin skin test (TST) was evaluated in the context of IGRA studies. In addition, the rates of indeterminates of both IGRAs were assessed. The pooled sensitivity of TST was 70% (95% CI, 0.67-0.72) compared with 81% (95% CI, 0.78-0.83) for the QFT-IT and 88% (95% CI, 0.85-0.90) for the T-Spot.TB. Sensitivity increased to 84% (95%CI, 0.81-0.87) and 89% (95% CI, 0.86-0.91) for the QFT-IT and T-Spot.TB, respectively, when restricted to performance in developed countries. In contrast, specificity of the QFT-IT was 99% (95% CI, 0.98-1.00) vs 86% for the T-Spot.TB (95% CI, 0.81-0.90). The pooled rate of indeterminate results was low, 2.1% (95% CI, 0.02-0.023) for the QFT-IT and 3.8% (95% CI, 0.035-0.042) for the T-Spot.TB, increasing to 4.4% (95% CI, 0.039-0.05) and 6.1% (95% CI, 0.052-0.071), respectively, among immunosuppressed hosts. The newest commercial IGRAs are superior, in comparison with the TST, for detecting confirmed active TB disease, especially when performed in developed countries.

Solitary pulmonary nodules caused by Mycobacterium tuberculosis and Mycobacterium avium complex

Few studies have compared the clinical and radiographic findings of tuberculomas to those of solitary pulmonary nodules (SPNs) caused by Mycobacterium avium complex (MAC). We retrospectively analyzed clinical and radiographic findings from 26 patients with tuberculomas and 15 patients with SPNs caused by MAC. Median SPN size was 22 mm. In 26 patients (63%), the SPN was detected during a routine health checkup or evaluation of organs other than lungs. Patients with SPNs due to MAC were slightly older (median = 59 years) compared with those with tuberculomas (median = 50 years; P = 0.044). When we compared computed tomography (CT) features between patients with tuberculomas and patients with MAC, no significant differences were found in SPN location or the presence of calcification, cavitation, central low attenuation, and the satellite lesions. Although the maximum standardized uptake values were slightly higher in patients with SPNs due to MAC (median = 8.5) compared with those with tuberculomas (median = 2.2), this difference was not significant (P = 0.053). Of the 15 patients with SPNs due to MAC, 10 were initially diagnosed with "tuberculoma" and administered antituberculosis medication. MAC pulmonary disease should be considered in the differential diagnosis of SPNs, even when encountered in geographic regions with a high prevalence of pulmonary tuberculosis.

Update on cutaneous manifestations of infectious diseases

Many emerging pathogens present in the skin and are of interest to dermatologists. Recent epidemics of measles, avian flu, and SARS demonstrated how an organism can rapidly spread worldwide because of airline travel. Travelers are often contagious before they are aware that they have the disease, contributing to the spread. This article reviews bacterial, mycobacterial, fungal, and viral pathogens important to dermatologists.

Screening for tuberculosis infection in spanish healthcare workers: Comparison of the QuantiFERON-TB gold in-tube test with the tuberculin skin test

OBJECTIVE

The risk of latent tuberculosis (LTBI) in healthcare workers (HCWs) is high. Until recently, the tuberculin skin test (TST) was the only diagnostic test available for Mycobacterium tuberculosis infection. A new enzyme-linked immunosorbent assay test, the QuantiFERON-TB Gold (QFT-G) test, was recommended by the US Centers for Disease Control and Prevention as an alternative test for the diagnosis of LTBI in HCWs. The purpose of our study was to compare the TST and the QFT-G test in Spanish HCWs in order to improve procedures for the detection of LTBI.

METHODS

A cross-sectional study with blinded comparison of TST and QFT-G test results was carried out among 134 HCWs at an 800-bed Spanish university hospital. The level of interferon-gamma production stimulated by the QFT-G test was measured. A concentration of at least 0.35 IU/mL was considered a positive result. An induration of at least 5 mm in non-BCG-vaccinated or at least 15 mm in BCG-vaccinated HCWs for the TST was considered positive.

RESULTS

Of the 134 HCWs included (mean age, 33.4 years; 101 [75.4%] women; 47 [35.1%] BCG vaccinated), the LTBI prevalence diagnosed with any test was 11.2% (95% confidence interval, 6.6%-18.1%), with the TST was 8.96%, and with the QFT-G test was 5.97% (nonsignificant differences). The QFT-G test value was higher in subjects with TST induration of at least 15 mm than in subjects with TST induration of less than 15 mm (P < .001). Overall agreement between the results of the two tests was found in 94% of HCWs (kappa = 0.56), but agreement was only 59% in HCWs who had a positive result for both tests. Disagreement was present in the results found for 5% of HCWs.

CONCLUSIONS

Few studies have compared both tests in populations with high M. tuberculosis exposure but low BCG vaccination prevalence. Agreement between both tests is high, especially among negative results. Studies are needed to clarify the reasons for disagreement and to establish the best TST and QFT-G test cutoff point.

Nontuberculous mycobacterial skin infections: recognition and management

Mycobacterial organisms have re-emerged as an important cause of infectious disease worldwide. Both tuberculosis and nontuberculous mycobacterial infections remain endemic in many parts of the world and are becoming more common in patients with iatrogenic immunosuppression and HIV infection. The nontuberculous mycobacteria, often referred to as mycobacteria other than tuberculosis (MOT), are of special significance to the dermatologist because they often present in the skin, typically after exposure to an aqueous environment. Presentations range from indolent nodules with sporotrichoid spread to acute suppurative folliculitis and abscess formation. Infection with MOT should be considered whenever routine bacterial cultures are negative. Cultures should be obtained, but empiric therapy must often be started while cultures are pending. Some data suggest that clarithromycin may be the best initial empiric therapy.

Usefulness of interferon-gamma release assays for diagnosing TB infection and problems with these assays

The specificity of the tuberculin skin test (TST) in the diagnosis of tuberculosis infection is seriously compromised because of extensive use of the bacille Calmette-Guérin (BCG) vaccination. The interferon-gamma release assay (IGRA), a new diagnostic using Mycobacterium tuberculosis-specific antigens has been introduced in response to these needs. In this review, published findings on the performance of the QuantiFERON-TB (QFT), one of the IGRA formats, are summarized and discussed. In addition to its high specificity, the QFT has considerably high sensitivity, comparable with or superior to that of the TST, if applied to patients with active tuberculosis as a surrogate of latent tuberculosis infection. When applied to patients with immunosuppression, such as aging patients, or those with HIV infection, those with immunosuppressive drug therapies, or those with renal hemodialysis, QFT is shown to be more robust than the TST. As regards the dynamics of QFT responses to chemotherapy, there are many reports showing a decrease in responses during the treatment, which indicates the possibility that QFT could be used as a tool for monitoring the progress of treatment. However, there are discordant reports that warrant further study.

Role of interferon gamma release assay in active TB diagnosis among HIV infected individuals

Background

A rapid and specific test is urgently needed for tuberculosis (TB) diagnosis especially among human immunodeficiency virus (HIV) infected individuals. In this study, we assessed the sensitivity of Interferon gamma release assay (IGRA) in active tuberculosis patients who were positive for HIV infection and compared it with that of tuberculin skin test (TST).

Methodology/Principal Findings

A total of 105 HIV-TB patients who were naïve for anti tuberculosis and anti retroviral therapy were included for this study out of which 53 (50%) were culture positive. Of 105 tested, QuantiFERON-TB Gold in-tube (QFT-G) was positive in 65% (95% CI: 56% to 74%), negative in 18% (95% CI: 11% to 25%) and indeterminate in 17% (95% CI: 10% to 24%) of patients. The sensitivity of QFT-G remained similar in pulmonary TB and extra-pulmonary TB patients. The QFT-G positivity was not affected by low CD4 count, but it often gave indeterminate results especially in individuals with CD4 count <200 cells/µl. All of the QFT-G indeterminate patients whose sputum culture were positive, showed ≤0.25 IU/ml of IFN-γ response to phytohemagglutinin (PHA). TST was performed in all the 105 patients and yielded the sensitivity of 31% (95% CI: 40% to 22%). All the TST positives were QFT-G positives. The sensitivity of TST was decreased, when CD4 cell counts declined.

Conclusions/Significance

Our study shows neither QFT-G alone or in combination with TST can be used to exclude the suspicion of active TB disease. However, unlike TST, QFT-G yielded fewer false negative results even in individuals with low CD4 count. The low PHA cut-off point for indeterminate results suggested in this study (≤0.25 IU/ml) may improve the proportion of valid QFT-G results.