Abstract
The objective of this study was to compare the sensitivity and specificity of smear and culture methods with rapid serological EIA myco kits manufactured by Omega diagnostics, for the early detection of Mycobacterium tuberculosis (MTB) complex. Sera from various categories of smear and culture results were compared with the result of 38KDa, 16KDa and purified protein for IgA, IgM and IgG antibodies with sensitivity of 4%, 24% and 76%, respectively and with specificity of100% for IgG in Smear and Culture Positive (S+)C+)) category. The sensitivity of the test improved to a level of 80% for IgG + IgA without affecting the specificity. A combination of IgG + IgA and IgM further improved the sensitivity to 88% but reduced the specificity to 91%. Amongst the S–)C+) and S–)C–) 64% and 14.7% were positive for IgG respectively. The predictive value of the kit using S+)C+) subject was 96%. For all culture positivity (n=78), there was 2.6%, 33.3% and 71.8% sensitivity for IgA, IgM and IgG respectively. IgA +IgG and IgA + IgM + IgG combination gave 74.4% and 84.6% sensitivity respectively with the same level of specificity. Fifty-five percent of culture positive subjects were found to be MTB complex positive by routine biochemical tests, while 40% through PATHOZYME TB COMPLEX PLUS kit (high positive (H+)) values). When high positivity is combined with low positivity of the same kit (H+) + L+)), 65% of the isolates were found to be MTB complex. Our study showed 88% sensitivity and 91% specificity for combined IgA + IgM + IgG antibodies recorded for MTB (S+)C+) group) and 85% sensitivity and 91% specificity for all culture positives. Our study has demonstrated that the myco kits and TB complex plus kit produced by Omega Diagnostics are a good tool for specific, early and rapid identification of active tuberculosis for both diagnostic and epidemiological purposes.
Key Words: Tuberculosis, diagnosis, comparative, specificity, sensitivity, culture and serological technique.
Afr. J. Clin. Exper. Microbiol. 2004; 5(2): 182 – 188.