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Limited added value of T-SPOT.TB blood test in diagnosing active TB: a prospective bayesian analysis.

Boyd, AE; Ashcroft, A; Lipman, M; Bothamley, GH; (2011) Limited added value of T-SPOT.TB blood test in diagnosing active TB: a prospective bayesian analysis. J Infect , 62 (6) pp. 456-461. 10.1016/j.jinf.2011.04.003.

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Abstract

OBJECTIVES: To determine the diagnostic value of a blood interferon-gamma release assay in suspected active tuberculosis (TB). METHODS: 136 subjects with suspected pulmonary TB (pTB) at a single London centre with intermediate TB incidence, were clinically graded into low (<25%), medium, or high (>75%) likelihood of active pTB and then tested by T-SPOT®.TB assay. The diagnosis was confirmed by culture (n = 33), treatment response (n = 13) or a firm alternative diagnosis (n = 90). RESULTS: Overall, the T-SPOT.TB sensitivity was 74% (95% confidence intervals 60-84%), positive predictive value (PPV) 56% (43-68%), negative predictive value (NPV) 83% (71-90%), positive likelihood ratio (PLR) 1.75 and negative likelihood ratio (NLR) 0.45. Results for high pTB likelihood subjects: PPV 100%, NPV 25% (7-60%), PLR >69, NLR 0.31. Results for intermediate pTB likelihood subjects: PPV 67% (41-85%), NPV 88% (65-96%), PLR 2.39, NLR 0.26. Results for low pTB likelihood subjects: PPV 15% (6-34%), NPV 92% (79-97%), PLR 1.23, NLR 0.80. False negatives occurred in 24% of cases of active tuberculosis (4 smear and culture-positive, 3 smear negative and culture-positive, and 4 culture negative). CONCLUSIONS: The predictive values and likelihood ratios show the T-SPOT.TB test does not assist in confidently confirming or excluding active TB, regardless of the pre-test probability of disease.

Type: Article
Title: Limited added value of T-SPOT.TB blood test in diagnosing active TB: a prospective bayesian analysis.
Location: England
DOI: 10.1016/j.jinf.2011.04.003
Keywords: Bayes Theorem, Clinical Laboratory Techniques, False Negative Reactions, Female, Humans, Immunoassay, Interferon-gamma, London, Male, Predictive Value of Tests, Prospective Studies, Sensitivity and Specificity, Tuberculosis
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine > Respiratory Medicine
URI: http://discovery.ucl.ac.uk/id/eprint/1384668
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