The accuracy of sputum smear microscopy, the tuberculosis case-finding method in the Abia State TB Control Programme has never been assessed due to lack of culture facilities. To assess the accuracy of sputum smear microscopy in routine control programme conditions in Abia State, sputum samples from patients undergoing investigation for tuberculosis were analyzed using Ziehl-Neelsen staining technique for sputum smear microscopy and culture on Löwenstein-Jensen medium as reference standard. Out of 150 participants tested, 51 were smear-positive for acid fast bacilli (positivity rate, 34.0 %, 51/150) while 79 were culture positive for Mycobacterium tuberculosis complex and 12 for non-tuberculous mycobacteria (NTM). Thirty-seven of the 79 culture positive for M. tuberculosis were smear positive giving a ratio of smear to culture positivity of 46.84%. Forty-two (42.4%) of the 99 smear negative cases were culture positive for M. tuberculosis. The sensitivity of smear microscopy was 50.0% (95%CI=39.0-61.0) and specificity was 92.3% (95% CI=86.4-98.2). The prevalence of HIV/TB coinfection among the study participants was 48% (12/25). Although the case-detection rate of smear microscopy was moderate in this study, the large proportion of TB patients missed by smear microscopy is a cause for concern and requires concerted effort to improve the sensitivity of smear microscopy. Introduction of more sensitive diagnostic methods like culture also need to be considered.

Correspondence to: E. O. Ekundayo (emma_ekundayo@yahoo.com). ABSTRACTThe Clinotech TB Screen test, a 3 rd generation multi-antigen rapid chromatographic immunoassay for detection of IgG antibodies in serum against recombinant protein antigens 38kDa, 16kDa and 6kDa, was assessed for its diagnostic potential for diagnosis of active pulmonary TB in routine TB control programme in Abia State, Nigeria. The overall sensitivity and specificity of Clinotech TB Screen test were 24.1% and 87.8% (95% Confidence intervals [CI]: 14.7-33.5% and 80.6-95.0%) respectively. The positive and Negative Predictive Values (PPV and NPV) were 79.2% and 37.5% respectively. The performance of the test was inferior to that of the sputum smear microscopy which had a sensitivity of 50.0% (95% CI, 39.0%-61.0%) and specificity of 92.3(95% CI: 86.4-98.2%). In 37 culture positive smear positive PTB cases, Clinotech TB Screen test was positive in 18(48.65%). The rapid test showed a very low degree of sensitivity in smear -negative culture positive PTB cases; detecting just one (2.38%) out of 42 cases. These results indicate that the diagnostic value of Clinotech TB Screen test for routine diagnosis of PTB in this setting is limited.