Smear-positive pulmonary tuberculosis and AFB examination practices according to the standard checklist of WHO’s tuberculosis laboratory assessment tool in three governmental hospitals, Eastern Ethiopia

Abstract

Background

Using the Directly Observed Treatment-Short course (DOTS) program the World Health Organization’s global target was to detect 70% of new sputum-smear positive PTB cases. Smear positive PTB cases are more infectious than the smear negative cases. The TB case detection rate remains very low in Ethiopia, but there are increases in smear-negative PTB diagnosis which could be attributed to several factors including poor quality of sputum smear-microscopy.

Methods

A five years retrospective record review of data between September, 2007 and August, 2012 and an in-depth assessment of AFB staining practices of sputum smear using a standard checklist were made. The proportion of smear positive cases relative to overall Acid Fast Bacilli (AFB) screened was determined over a five year period to indicate the overall prevalence and the trend. Odds ratio with 95 percent confidence interval was calculated for categorical variables using multivariate Logistic Regression model to assess the strength of association.

Result

A total of 1266 individuals’ data were reviewed. The majority of the study participants were male, 704 (55.6%), and rural residents, 690 (54.5%). The overall prevalence rate of smear positive PTB was 21.6%. Age categories between 15–24 and 25–34 years were independent predictors of smear positive PTB with adjusted odds ratio of 2.246 [95% CI (1.098-4.597)] and 2.267 [95% CI (1.107-4.642)], respectively. More males were affected by PTB than females with an adjusted odds ratio of 1.426 [95% CI (1.083-1.879)]. An in-depth interview with the respective laboratory chiefs showed that quality control measures for sputum smear microscopy were used at different levels of the testing activities; however, equipment function verification as a quality control measure was not accomplished regularly in all of the study hospital laboratories.

Conclusion

The smear positive PTB case detection rate indicated in this study is significantly lower than the countries which met the 70% target of the World Health Organization. Lack of feedback mechanisms in the External Quality Assurance schemes of sputum smear microscopy render the opportunity for improvement difficult; Serial sputum examination showed a considerable rate of positivity in the second sputum sample when compared with the others.