Serial testing using interferon- release assays in nursing students in India

European Respiratory Journal (Impact Factor: 7.64). 04/2014; 44(1). DOI: 10.1183/09031936.00011914
Source: PubMed

ABSTRACT To the Editor:We have previously shown that Indian healthcare workers have higher prevalence of latent tuberculosis infection (LTBI) and are at increased risk for new infection (1-4). Interferon-γ release assays (IGRAs) have been introduced as an alternative to the tuberculin skin test (TST) for diagnosing LTBI in healthcare workers and other high-risk groups. They have logistical advantages over the TST and will not cross-react with the bacille Calmette Guérin vaccine. IGRAs are now being widely used for screening healthcare workers (5), yet recent reports indicate that switching from TST to IGRAs for the serial testing of healthcare workers may result in increased rates of test conversions and reversions (3, 6-8). Most of these studies are from low tuberculosis (TB) incidence settings, with limited opportunity for nosocomial TB exposure; as a result, the increased conversion rates are considered false-positive test conversions, making it difficult for clinicians to interpret IGRA test conversions in these settings (9). It remains unclear whether IGRA conversions are associated with TB exposure in high TB incidence settings where unprotected exposure to infectious TB patients is more common among healthcare workers.To evaluate whether IGRA conversions may represent new cases of LTBI, in a high TB incidence setting, in the.

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Available from: DJ Christopher, Sep 18, 2015
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    ABSTRACT: Objectives: To evaluate the T-cell interferon (IFN)-γ response to Mycobacterium tuberculosis-specific antigens during latent tuberculosis infection (LTBI) therapy in candidates for tumor necrosis factor-α inhibitors (TNFi). Methods: 1490 Patients were screened for LTBI. One-hundred and sixty-six of them were treated for LTBI and followed-up with QuantiFERON-TB Gold (QFT-IT) testing at baseline (T0) and therapy completion (T1); 92 subjects were also tested 3-6 months after therapy completion (T2). Results: At T1 the QFT-IT reversion and conversion rates were 24% (27/111) and 18% (10/55), respectively. By multivariate analysis, the likelihood of reversion significantly decreased with older age (>50-60), larger TST size (>15 mm) and higher IFN-γ value at T0 (>1 IU/ml); the likelihood of conversion increased with higher IFN-γ levels at T0 (1 IU/ml) and in female patients. Quantitative data among those who scored QFT-IT-positive at T0 showed a decreasing trend of IFN-γ levels between T0 and T1 that reached statistical significance when T0 was compared to T2, and T1 to T2. Conclusions: The data confirm the difficulty of interpreting the modulation of IFN-γ levels during LTBI therapy. Currently, there is no evidence to support the use of QFT-IT in the clinical practice of monitoring LTBI treatment in candidates for TNFi.
    The Journal of infection 10/2012; 66(4). DOI:10.1016/j.jinf.2012.10.017 · 4.44 Impact Factor
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    ABSTRACT: Nurses in developing countries are frequently exposed to infectious tuberculosis (TB) patients, and have a high prevalence of TB infection. To estimate the incidence of new TB infection, we recruited a cohort of young nursing trainees at the Christian Medical College in Southern India. Annual tuberculin skin testing (TST) was conducted to assess the annual risk of TB infection (ARTI) in this cohort. 436 nursing students completed baseline two-step TST testing in 2007 and 217 were TST-negative and therefore eligible for repeat testing in 2008. 181 subjects completed a detailed questionnaire on exposure to tuberculosis from workplace and social contacts. A physician verified the questionnaire and clinical log book and screened the subjects for symptoms of active TB. The majority of nursing students (96.7%) were females, almost 84% were under 22 years of age, and 80% had BCG scars. Among those students who underwent repeat testing in 2008, 14 had TST conversions using the ATS/CDC/IDSA conversion definition of 10 mm or greater increase over baseline. The ARTI was therefore estimated as 7.8% (95%CI: 4.3-12.8%). This was significantly higher than the national average ARTI of 1.5%. Sputum collection and caring for pulmonary TB patients were both high risk activities that were associated with TST conversions in this young nursing cohort. Our study showed a high ARTI among young nursing trainees, substantially higher than that seen in the general Indian population. Indian healthcare providers and the Indian Revised National TB Control Programme will need to implement internationally recommended TB infection control interventions to protect its health care workforce.
    PLoS ONE 10/2011; 6(10):e26199. DOI:10.1371/journal.pone.0026199 · 3.23 Impact Factor
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    ABSTRACT: Rationale: Interferon gamma release assays (IGRAs) are alternatives to tuberculin skin testing (TST) for diagnosis of latent tuberculosis infection. Limited data suggest IGRAs may not perform well for serially testing healthcare workers (HCWs). Objective:Determine performance characteristics ofIGRAs vs. TST for serially testing HCWs. Methods:A longitudinal study involving 2563 HCWs undergoing occupationaltuberculosis screening at four healthcare institutions in the United States where the average tuberculosis case rate ranged from 4 to 9/100,000 persons.QuantiFERON®-TB Gold in-Tube (QFT-GIT), T-SPOT®.TB (T-SPOT), and TST were performed at baseline and every 6 months for 18 months between February 2008 and March 2011. Measurements and Main Results: 2418 HCWs completed baseline testing, which was positive for 125 (5.2%) by TST, 118 (4.9%) by QFT-GIT, and 144 (6.0%) by T-SPOT. A baseline positive TST with negative IGRAs was associated with Bacille Calmette- Guérin (BCG) vaccination (OR 25.1 [95% CI15.5, 40.5] vs. no BCG).Proportions of participants with test conversion during the study period were 138/2263 (6.1%) for QFTGIT, 177/2137 (8.3%) for T-SPOT, and 21/2293 (0.9%) for TST (p<0.001 for QFT-GIT vs. TST and for T-SPOT vs. TST; p=0.005 for QFT-GIT vs. T-SPOT). 81/106 (76.4%) QFT-GIT and 91/118 (77.1%) T-SPOT converters were negative when retested 6 months later. There was negative/positive discordance for 15/170 (8.8%) participants by QFTGIT and 19/151 (12.6%) by T-SPOT when blood was drawn two weeks later. Conclusions:Most conversions among HCWs in low TB incidence settings appear to be false-positives and these occurred 6-9 times more frequently with IGRAs than TST;repeat testing of apparent converters is warranted.
    American Journal of Respiratory and Critical Care Medicine 12/2013; 189(1). DOI:10.1164/rccm.201302-0365OC · 13.00 Impact Factor
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