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Comparison of same day diagnostic tools including Gene Xpert and unstimulated IFN-? for the evaluation of pleural tuberculosis: a prospective cohort study.

ABSTRACT: BACKGROUND: The accuracy of currently available same-day diagnostic tools (smear microscopy and conventional nucleic acid amplification tests) for pleural tuberculosis (TB) is sub-optimal. Newer technologies may offer improved detection. METHODS: Smear-microscopy, adenosine deaminase (ADA), interferon gamma (IFN-?), and Xpert MTB/RIF [using an unprocessed (1 ml) and centrifuged (~20 ml) sample] test accuracy was evaluated in pleural fluid from 103 consecutive patients with suspected pleural TB. Culture for M.tuberculosis and/or histopathology (pleural biopsy) served as the reference standard. Patients were followed prospectively to determine their diagnostic categorisation. RESULTS: Of 93 evaluable participants, 40 had definite-TB (reference positive), 5 probable-TB (not definite but treated for TB) and 48 non-TB (culture and histology negative, and not treated for TB). Xpert MTB/RIF sensitivity and specificity (95% CI) was 22.5% (12.4 - 37.6) and 98% (89.2 - 99.7), respectively, and centrifugation did not improve sensitivity (23.7%). The Xpert MTB/RIF internal positive control showed no evidence of inhibition. Biomarker specific sensitivity, specificity, PPV, and NPVs were: ADA (48.85 IU/L; rule-in cut-point) 55.3% (39.8 - 69.9), 95.2% (83.9 - 98.7), 91.4 (73.4 - 95.4), 69.7% (56.7 - 80.1); ADA (30 IU/L; clinically used cut-point) 79% (63.7 - 89), 92.7% (80.6 - 97.5), 91.0 (73.4 - 95.4), 82.7% (69.3 - 90.1); and IFN-? (107.7 pg/ml; rule-in cut-point) 92.5% (80.2 - 97.5), 95.9% (86.1 - 98.9), 94.9% (83.2 - 98.6), 93.9% (83.5 - 97.9), respectively (IFN-? sensitivity and NPV better than Xpert [p < 0.05] and rule-in ADA [p < 0.05]). CONCLUSION: The usefulness of Xpert MTB/RIF to diagnose pleural TB is limited by its poor sensitivity. IFN-? is an excellent rule-in test and, compared to ADA, has significantly better sensitivity and rule-out value in a TB-endemic setting.

SUBMITTER: Meldau R

PROVIDER: S-EPMC4108018 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Comparison of same day diagnostic tools including Gene Xpert and unstimulated IFN-γ for the evaluation of pleural tuberculosis: a prospective cohort study.

Meldau Richard R Peter Jonny J Theron Grant G Calligaro Greg G Allwood Brian B Symons Greg G Khalfey Hoosain H Ntombenhle Gina G Govender Ureshnie U Binder Anke A van Zyl-Smit Richard R Dheda Keertan K

BMC pulmonary medicine 20140408

<h4>Background</h4>The accuracy of currently available same-day diagnostic tools (smear microscopy and conventional nucleic acid amplification tests) for pleural tuberculosis (TB) is sub-optimal. Newer technologies may offer improved detection.<h4>Methods</h4>Smear-microscopy, adenosine deaminase (ADA), interferon gamma (IFN-γ), and Xpert MTB/RIF [using an unprocessed (1 ml) and centrifuged (~20 ml) sample] test accuracy was evaluated in pleural fluid from 103 consecutive patients with suspected ...[more]

PMID: 24708530

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Project description:BackgroundSputum smear microscopy is the most widely available diagnostic test for pulmonary tuberculosis in countries with a high burden of the disease. Improving its accuracy is crucial to achievement of case-detection targets established by the Millennium Development Goals. Unfortunately, many patients are unable to submit all of the specimens needed for examination or to return for treatment because standard sputum collection and reporting requires several clinic visits. To inform policy recommendations by a WHO-convened Expert Group, we aimed to assess the accuracy of sputum smear examination with strategies for obtaining sputum on 1 day compared with strategies for obtaining sputum over 2 days.MethodsWe did a systematic review and meta-analysis of research articles comparing the accuracy of front-loaded or same-day microscopy and standard sputum smear microscopy for diagnosis of culture-confirmed pulmonary tuberculosis. We searched Medline, Embase, Biosis, and Web of Science for articles published between Jan 1, 2005, and Feb 14, 2012. Two investigators identified eligible articles and extracted data for individual study sites. We generated pooled summary estimates (95% CIs) for sensitivity and specificity by use of random-effects meta-analysis when four or more studies were available.FindingsWe identified eight relevant studies from five articles enrolling 7771 patients with suspected tuberculosis in low-income countries. Compared with the standard approach of examination of two smears with Ziehl-Neelsen light microscopy over 2 days, examination of two smears taken on the same day had much the same sensitivity (64% [95% CI 60 to 69] for standard microscopy vs 63% [58 to 68] for same-day microscopy) and specificity (98% [97 to 99] vs 98% [97 to 99]). We noted similar results for studies employing light-emitting diode fluorescence microscopy and for studies examining three smears, whether they were compared with two-smear strategies or with one another.InterpretationSame-day sputum smear microscopy is as accurate as standard smear microscopy. Data from tuberculosis programmes are needed to document the changes required in the health system to successfully implement the strategy and understand its effects.FundingWHO and US National Institutes of Health.

Dataset Information

Comparison of same day diagnostic tools including Gene Xpert and unstimulated IFN-? for the evaluation of pleural tuberculosis: a prospective cohort study.

Publications

Comparison of same day diagnostic tools including Gene Xpert and unstimulated IFN-γ for the evaluation of pleural tuberculosis: a prospective cohort study.

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