Research Article: Performance evaluation of tuberculosis smear microscopists working at rechecking laboratories in Ethiopia

Date Published: April 21, 2017

Publisher: AOSIS

Author(s): Habtamu Asrat, Abebaw Kebede, Abnet Abebe, Abyot Meaza, Getinet Hailu, Adinew Desale, Andargachew Gashu, Wondwossen Kassa, Tesfaye Mekonnen, Ebisea Abose, Feven Girmachew, Dereje Yenealem, Achamyeleh Mulugeta, Gonfa Ayana, Kassu Desta.


Tuberculosis is an infectious disease caused by the bacillus Mycobacterium tuberculosis. According to the Ethiopian Federal Ministry of Health’s 2013–2014 report, the tuberculosis case detection rate was 53.7%, which was below the target of 81% set for that year.

This study assessed the performance of tuberculosis smear microscopists at external quality assessment rechecking laboratories in Ethiopia.

A cross-sectional study was conducted at 81 laboratories from April to July 2015. Panel slides were prepared and validated at the National Tuberculosis Reference Laboratory. The validated panel slides were used to evaluate the performance of microscopists at these laboratories compared with readers from the reference laboratory.

A total of 389 external quality assessment rechecking laboratory microscopists participated in the study, of which 268 (68.9%) worked at hospitals, 241 (62%) had more than five years of work experience, 201 (51.7%) held Bachelors degrees, and 319 (82%) reported tuberculosis smear microscopy training. Overall, 324 (83.3%) participants scored ≥ 80%. Sensitivity for detecting tuberculosis bacilli was 84.5% and specificity was 93.1%. The overall percent agreement between participants and reference readers was 87.1 (kappa=0.72). All 10 slides were correctly read (i.e., scored 100%) by 80 (20.6%) participants, 156 (40.1%) scored 90% – 95%, 88 (22.6%) scored 80% – 85% and 65 (16.7%) scored below 80%. There were 806 (20.7%) total errors, with 143 (3.7%) major and 663 (17%) minor errors.

The overall performance of participants in reading the slides showed good agreement with the reference readers. Most errors were minor, and the ability to detect tuberculosis bacilli can be improved through building the capacity of professionals.

Partial Text

Tuberculosis is an infectious disease caused by the bacillus Mycobacterium tuberculosis. It remains a major global health problem, responsible for ill health among millions of people each year.1,2,3 It is the second leading cause of death among all infectious diseases worldwide after HIV.1,3 According to the 2014 World Health Organization Global Tuberculosis Report, there were nine million new tuberculosis cases and 1.5 million tuberculosis deaths (1.1 million among HIV-negative people and 0.4 million among HIV-positive people) in 2013.1 One quarter of global cases and deaths occurred in the African Region,1 and Ethiopia ranked 10th in tuberculosis incidence among 22 high-burden countries.1,4

This cross-sectional study evaluated the performance of tuberculosis smear microscopists working at EQA rechecking laboratories and the status of the respective laboratories. In this study, the overall agreement of participants with reference readers for reading the validated slides was 87.1% (kappa=0.72), which was good agreement based on kappa statistics.14 However, lower agreement was observed when compared with a different study conducted in Southern Ethiopia, which found 96.8% agreement (kappa=0.936),15 and a study done in the town of Hawassa, Ethiopia, which found 95.2% agreement (kappa=0.73).16 When compared with a study done in the East and West Amhara regions of Ethiopia, higher agreement was also observed (98.4% in East Amhara and 96.5% in West Amhara [kappa=0.92]).17,18 Thus, performance in our study was slightly lower than in similar studies conducted in other parts of Ethiopia. This may have been due to the large number of laboratories and/or laboratory professionals included in our study, which was more of a nationwide study with wider representation. This may have made our study more prone to lower performance.




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