Case-Detection Rate of Direct Sputum Smear Microscopy for Diagnosis of Pulmonary Tuberculosis in Abia State, Nigeria

Abstract

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.

Effectiveness of Contact Tracing of Index Tuberculosis Cases in Nigeria

“…[17] opined that poor health seeking behaviors among presumptive TB cases was responsible for delayed diagnosis of TB. In addition, [18] noted that TB case detection is affected by limitation of Ziehl Nelson techniques as 50% of the cases are missed due to low sensitivity. More so, [19] noted that TB case detection in Nigeria has been suboptimal due to low awareness by relevant stakeholders.…”

“…Many factors such as poor access, stigmatization, inadequate human resources and insufficient direct observed treatment and diagnostic centers has been implicated as main causes of low case detection [16]. In-addition, [18] opined that TB case detection is affected by limitation of Ziehl-neelson techniques as 50% of the cases are miised. More so, [19] noted that TB case detection in Nigeria has been suboptimal stressing that low awareness has been a complementary contributing factor.…”