Dataset Information

Diagnosis and follow-up of treatment of latent tuberculosis; the utility of the QuantiFERON-TB Gold In-tube assay in outpatients from a tuberculosis low-endemic country.

ABSTRACT:

Background

Interferon-gamma (IFN-gamma) Release Assays (IGRA) are more specific than the tuberculosis skin test (TST) in the diagnosis of latent tuberculosis (TB) infection (LTBI). We present the performance of the QuantiFERON-TB Gold In-tube (QFT-TB) assay as diagnostic test and during follow-up of preventive TB therapy in outpatients from a TB low-endemic country.

Methods

481 persons with suspected TB infection were tested with QFT-TB. Thoracic X-ray and sputum samples were performed and a questionnaire concerning risk factors for TB was filled. Three months of isoniazid and rifampicin were given to patients with LTBI and QFT-TB tests were performed after three and 15 months.

Results

The QFT-TB test was positive in 30.8% (148/481) of the total, in 66.9% (111/166) of persons with origin from a TB endemic country, in 71.4% (20/28) previously treated for TB and in 100% (15/15) of those diagnosed with active TB with no inconclusive results. The QFT-TB test was more frequently positive in those with TST > or = 15 mm (47.5%) compared to TST 11-14 mm (21.3%) and TST 6-10 mm (10.5%), (p < 0.001). Origin from a TB endemic country (OR 6.82, 95% CI 1.73-26.82), recent stay in a TB endemic country (OR 1.32, 95% CI 1.09-1.59), duration of TB exposure (OR 1.59, 95% CI 1.14-2.22) and previous TB disease (OR 11.60, 95% CI 2.02-66.73) were all independently associated with a positive QFT-TB test. After preventive therapy, 35/40 (87.5%) and 22/26 (84.6%) were still QFT-TB positive after three and 15 months, respectively. IFN-gamma responses were comparable at start (mean 6.13 IU/ml +/- SD 3.99) and after three months (mean 5.65 IU/ml +/- SD 3.66) and 15 months (mean 5.65 IU/ml +/- SD 4.14), (p > 0.05).

Conclusion

Only one third of those with suspected TB infection had a positive QFT-TB test. Recent immigration from TB endemic countries and long duration of exposure are risk factors for a positive QFT-TB test and these groups should be targeted through screening. Since most patients remained QFT-TB positive after therapy, the test should not be used to monitor the effect of preventive therapy. Prospective studies are needed in order to determine the usefulness of IGRA tests during therapy.

SUBMITTER: Dyrhol-Riise AM

PROVIDER: S-EPMC2842274 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature

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Publications

Diagnosis and follow-up of treatment of latent tuberculosis; the utility of the QuantiFERON-TB Gold In-tube assay in outpatients from a tuberculosis low-endemic country.

Dyrhol-Riise Anne M AM Gran Gerd G Wentzel-Larsen Tore T Blomberg Bjørn B Haanshuus Christel Gill CG Mørkve Odd O

BMC infectious diseases 20100308

<h4>Background</h4>Interferon-gamma (IFN-gamma) Release Assays (IGRA) are more specific than the tuberculosis skin test (TST) in the diagnosis of latent tuberculosis (TB) infection (LTBI). We present the performance of the QuantiFERON-TB Gold In-tube (QFT-TB) assay as diagnostic test and during follow-up of preventive TB therapy in outpatients from a TB low-endemic country.<h4>Methods</h4>481 persons with suspected TB infection were tested with QFT-TB. Thoracic X-ray and sputum samples were perf ...[more]

PMID: 20210999

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Project description:BackgroundQuantiFERON-TB Gold In-Tube (QFT-GIT) is considered an alternative to the tuberculin skin test (TST) for the diagnosis of tuberculosis (TB) infection, but the programmatic impact of QFT-GIT implementation is largely unknown. In March, 2010, the Baltimore City Health Department (BCHD) introduced routine QFT-GIT testing for individuals referred to the TB program for suspected latent TB infection (LTBI).DesignRetrospective study comparing LTBI diagnosis and treatment during the 13 months before and after QFT-GIT implementation at the BCHD TB clinic.Results607 and 750 individuals were referred by community-providers for suspected LTBI in the pre- and post-QFT-GIT periods, respectively. Most individuals in the pre- and post-QFT-GIT periods were referred on the basis of a positive TST (597/607 [98%] vs. 690/750 [92%], respectively) and were foreign-born (363/607[59%] vs. 507/750[68%], respectively). BCHD performed QFT-GIT testing for 375/543 (69%) eligible individuals in the post-QFT-GIT period, of which 185 (49%) were positive, 178 (47%) were negative, 1 (0.25%) was indeterminate, and 11 (3%) did not yield results. Concordance of QFT-GIT with TST was low (183/352[52%]). Foreign-born individuals had higher proportions of QFT-GIT positivity (57%) than US-born individuals (36%; AOR 3.3 [95%CI 1.7-6.2]). Significantly fewer individuals received a final diagnosis of LTBI in the post-QFT-GIT period (397/567 [70%]) compared to the pre-QFT-GIT period (445/452 [98%], p<0.001). In the post-QFT-GIT period, only 230/399 (58%) of those receiving QFT-GIT testing had a final diagnosis of LTBI, while 167/168 (99%) of those without QFT-GIT testing were diagnosed with LTBI (p<0.001). There was no difference in treatment initiation between those with and without QFT-GIT testing (175/230 [76%]) vs. 133/167 [80%], respectively) in the post-QFT-GIT period.ConclusionQFT-GIT implementation for LTBI evaluation in a public health clinic significantly reduced the proportion of referred individuals in whom LTBI was diagnosed. QFT-GIT testing had no impact on treatment initiation or completion among those diagnosed with LTBI.

Project description:BackgroundThe QuantiFERON®-TB Gold In-Tube test (QFT-GIT) is a viable alternative to the tuberculin skin test (TST) for detecting Mycobacterium tuberculosis infection. However, within-subject variability may limit test utility. To assess variability, we compared results from the same subjects when QFT-GIT enzyme-linked immunosorbent assays (ELISAs) were performed in different laboratories.MethodsSubjects were recruited at two sites and blood was tested in three labs. Two labs used the same type of automated ELISA workstation, 8-point calibration curves, and electronic data transfer. The third lab used a different automated ELISA workstation, 4-point calibration curves, and manual data entry. Variability was assessed by interpretation agreement and comparison of interferon-? (IFN-?) measurements. Data for subjects with discordant interpretations or discrepancies in TB Response >0.05 IU/mL were verified or corrected, and variability was reassessed using a reconciled dataset.ResultsNinety-seven subjects had results from three labs. Eleven (11.3%) had discordant interpretations and 72 (74.2%) had discrepancies >0.05 IU/mL using unreconciled results. After correction of manual data entry errors for 9 subjects, and exclusion of 6 subjects due to methodological errors, 7 (7.7%) subjects were discordant. Of these, 6 (85.7%) had all TB Responses within 0.25 IU/mL of the manufacturer's recommended cutoff. Non-uniform error of measurement was observed, with greater variation in higher IFN-? measurements. Within-subject standard deviation for TB Response was as high as 0.16 IU/mL, and limits of agreement ranged from -0.46 to 0.43 IU/mL for subjects with mean TB Response within 0.25 IU/mL of the cutoff.ConclusionGreater interlaboratory variability was associated with manual data entry and higher IFN-? measurements. Manual data entry should be avoided. Because variability in measuring TB Response may affect interpretation, especially near the cutoff, consideration should be given to developing a range of values near the cutoff to be interpreted as "borderline," rather than negative or positive.

Project description:BackgroundWorld Health Organization (WHO) recommends systematic screening of high-risk populations, including household contacts (HHCs) of adult pulmonary tuberculosis (TB) patients, as a key strategy for elimination of TB. QuantiFERON-TB Gold In-Tube (QFT-GIT) assay and tuberculin skin test (TST) are two commonly used tools for the detection of latent tuberculosis infection (LTBI) but may yield differential results, affecting eligibility for TB preventive therapy.Materials and methodsA prospective cohort study of adult pulmonary TB patients and their HHCs were recruited in 2 cities of India, Pune and Chennai. HHCs underwent QFT-GIT (QIAGEN) and TST (PPD SPAN 2TU/5TU). A positive QFT-GIT was defined as value ?0.35 IU/ml and a positive TST as an induration of ?5 mm. A secondary outcome of TST induration ?10mm was explored. Proportion positive by either or both assays, discordant positives and negatives were calculated; test concordance was assessed using percentage agreement and kappa statistics; and risk factors for concordance and discordance including age categories were assessed using logistic regression. Sensitivity and specificity was estimated by latent class model.ResultsOf 1048 HHCs enrolled, 869 [median (IQR) age: 27 years (15-40)] had both TST and QFT-GIT results available and prevalence of LTBI by QFT-GIT was 54% [95% CI (51, 57)], by TST was 55% [95% CI (52, 58)], by either test was 74% [95% CI (71, 77) and by both tests was 35% [95% CI (31, 38)]. Discordance of TST+/QFT-GIT- was 21% while TST-/QFT-GIT+ was 26%. Poor to fair agreement occurred with TST 5mm or 10mm cutoff (60 and 61% agreement with kappa value of 0.20 and 0.25 respectively). Test agreement varied by age, TST strength and induration cut-off. In multivariate analysis, span PPD was a risk factor for QFT-GIT+ and TST- while absence of BCG scar was for TST+ and QFT-GIT-. Being employed and exposure to TB case outside the household case were associated with positivity by both the tests. Sensitivity of TST and QFT-GIT to diagnose LTBI was 77% and 69%. Probability of having LTBI was >90% when both tests were positive irrespective of exposure gradient.ConclusionPrevalence of LTBI among HHCs of adult pulmonary TB patients in India is very high and varies by test type, age, and exposure gradient. In our high TB burden setting, a strategy to treat all HHCs or a targeted strategy whereby an exposure index is used should be assessed in future preventive therapy and vaccine studies as HHCs have several factors that place them at high risk for progression to TB disease.

Dataset Information

Diagnosis and follow-up of treatment of latent tuberculosis; the utility of the QuantiFERON-TB Gold In-tube assay in outpatients from a tuberculosis low-endemic country.

Background

Methods

Results

Conclusion

Publications

Diagnosis and follow-up of treatment of latent tuberculosis; the utility of the QuantiFERON-TB Gold In-tube assay in outpatients from a tuberculosis low-endemic country.

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