Diagnostic performance and problem analysis of commercial tuberculosis antibody detection kits in China

BACKGROUND The diagnosis of bacterium-negative pulmonary tuberculosis (TB) and extra-pulmonary TB is challenging clinically. The detection of the anti-TB antibody has an important, auxiliary, clinical diagnostic value. Therefore, TB antibody detection kits should be screened and evaluated, and the reagents with the highest sensitivity and specificity should be chosen and used clinically. METHODS The diagnostic performance of 7 commercially available TB antibody detection kits (kits A, B, C, D, E, F and G) based on the gold immunoassay detection of immunoglobulin (Ig) G or IgM antibodies were simultaneously evaluated and compared in 62 TB cases and 56 non-TB cases in a laboratory. A retrospective analysis including 2549 cases was carried out to assess the clinical diagnosis values of bacteriological examinations and TB antibody tests (kits B and H used in the clinic). RESULTS The sensitivities of TB antibody kits A, B, C, D, E, F and G in the sera from 62 TB patients were 50.0%, 83.9%, 38.7%, 9.7%, 48.4%, 69.4% and 79.0%, respectively; the sensitivities in the sera from 24 smear-negative TB patients were 29.2%, 79.2%, 29.2%, 12.5%, 29.2%, 54.2% and 79.2%, respectively; the specificities in the sera from 56 non-TB patients were 73.2%, 25.0%, 85.7%, 96.4%, 78.6%, 78.6% and 50.0%, respectively. Of the 2549 clinically diagnosed cases, there were 1752 pulmonary TB cases, 505 extra-pulmonary TB cases, 87 old pulmonary TB cases and 205 non-TB cases. The positive results for smear, culture, TB antibody kit B and kit H in pulmonary TB cases were 39.8% (543/1365), 48.6% (372/765), 45.8% (802/1752) and 25.2% (442/1752), respectively; the results in extra-pulmonary TB cases were 3.4% (6/178), 5.8% (4/69), 35.4% (179/505), and 11.3% (57/505), respectively; the results in old pulmonary TB cases were 0% (0/64), 0% (0/30), 32.2% (28/87), and 9.2% (8/87), respectively; and the results in non-TB cases were 0% (0/121), 0% (0/56), 21.5% (44/205), and 2.4% (5/205), respectively. Of 624 smear-positive and/or culture-positive pulmonary TB cases, the sensitivities of antibody test kits B and H were 53.0% and 36.4%, respectively. Of 901 smear-negative and/or culture-negative pulmonary TB cases, the sensitivities of antibody test kits B and H were 42.5% and 19.0%, respectively. The positive rate of antibody detection in the bacterium-positive pulmonary TB cases was significantly higher than that in the bacterium-negative pulmonary TB cases (P < 0.05). CONCLUSIONS The colloidal gold-labeled TB antibody IgG detection assay is a simple, rapid and economical method that provides a better clinical auxiliary diagnosis value on TB, especially in smear-negative pulmonary TB and extra-pulmonary TB. The production, quality control, screening and evaluation of antibody detection kits are very important for its clinical application.