Diagnostic value of two rapid immunochromatographic tests for suspected tuberculosis diagnosis in clinical practice

Objective: To evaluate and compare the diagnostic value of two immunochromatographic tests for tuberculosis (ICT-TB) in clinical practice. Material and Method: The present extended cross-sectional study investigated suspected active TB patients at Maesai district hospital, and Lampang regional hospital between April 2009 and May 2010. Subjects underwent two commercial ICT-TB serum tests including: an endogenous ICT-TB, a local made test coated with 38 kD, 16 kD, and 6 kD antigens; and an exogenous ICT-TB, an imported test coated with 38 kD and lipoarabinomanan [LAM] antigens. All subjects received two months of follow up. Results: Of 401 patients, 146 (36.4%) had active TB, and 206 (51.4%) were HIV seropositive. An endogenous ICT-TB was superior to an exogenous ICT-TB in all diagnostic values measured except for specificity. In all patients, sensitivity was low, 35.6% (95% CI: 30.9-40.3) in an endogenous ICT-TB vs. 13.7% (95% CI: 10.3-17.1) in an exogenous ICT-TB. The specificity was high and equivalent in both tests, 93.7% (95%CI: 91.4-96.1). Higher diagnostic values were found among human immunodeficiency virus (HIV) seronegatives than in HIV seropositives when unadjusted for CD4+ cell count level. The likelihood ratios (LHR) were higher in patients with CD4+ cell count over 200 cells/μL than for the HIV seronegative group (LHR+ 7.6 vs. 4.8 in an endogenous ICT-TB, and 2.5 vs. 1.9 in an exogenous ICT-TB). Conclusion: For the present study setting, an endogenous ICT-TB can be a meaningful tool for first-line testing to rule in TB suspected cases. Subgroups of HIV seronegative and HIV seropositive patients with CD4+ cell count over 200 cells/μL may be expected to benefit most from the test. Keywords: Tuberculosis, HIV, Diagnostic test, Serological tests, Immunochromatographic tests