Immunochromatographic IgG/IgM test for rapid diagnosis of active tuberculosis

For rapid diagnosis and discrimination between active tuberculosis (TB) and other pulmonary diseases, we evaluated the clinical usefulness of detection of serum immunoglobulin IgG and IgM antibodies raised against mycobacterial 38-kDa, 16-kDa, and 6-kDa antigens by a commercial rapid immunochromatographic IgG/IgM test (Standard Diagnostics, South Korea) in 246 serum samples from three groups of patients: (i) 171 patients with active TB (128 with pulmonary TB [pTB] and 43 with extrapulmonary TB [epTB]), (ii) 73 patients with pulmonary non-TB diseases, and (iii) two leprosy patients. The sensitivities of IgG and IgM in patients with active TB (pTB and epTB) were 68.4% and 2.3%, respectively. IgG had the best performance characteristics, with sensitivities of 78.1% and 39.5% in sera from patients with active pTB and epTB, respectively, and a specificity of 100%. The sensitivities of IgM were poor and were similar for pTB and epTB (2.3%). In contrast, specificity was very elevated (100%). The combination of IgG with IgM did not improve its sensitivity. IgG-mediated responses against the mycobacterial 38-kDa, 16-kDa, and 6-kDa antigens might constitute a clinically useful tool for presumptive diagnosis and discrimination of active pTB from other pulmonary diseases. Moreover, based on its simplicity and rapidity of application, it could be a screening tool for active pTB in poorly equipped laboratories.