Diagnostic Yield of Serial Sputum Smear Microscopy Examination at Different Institutional Settings

Introduction: Number of samples and time of sputum collection has a great impact on the positivity yield of sputum smear microscopy examination. However, the impact is not yet extensively studied in Ethiopia. Therefore, the aim of this study was to assess the serials sputum sample collection impacts on the diagnostic yield of smear microscopy examination in Ethiopia at variation at different institutional settings. Methods: Institution based retrospective cohort study was conducted from October 2011 to March 2016. Two thousand four hundred sixty-three sputum smear microscopy positive result were reviewed from TB patient records. The collected data were computerized using Epi-info software and analyzed using SPSS version 20 software. Numerical summaries were used to describe the positivity yield of spot, morning and spot (SMS) sputum smear microscopy examination. Results: Of 2463 sputum smear-positive TB cases, 2384 (96.8%), 2458 (99.8%) and 2394 (97.2%) were detected by the first spot, morning and second spot sputum smear microscopy diagnosis, respectively. On the other hand, morning sputum smear results had the incremental yield of 74 (3.0%) and 64 (2.6%) from first spot sample and second spot sample, respectively. The results of 1892 (76.8%) TB cases were in agreement (detected) by three consecutive sputum specimen (SMS). Conclusion: The three consecutive sputum smear microscopy examination had 3% incremental yield compare to spot-spot (SS). The hospitals were participating in International External Quality Assurance Schemes (IEQAS) had better incremental (increased) yield in both SMS and SS approach compared to the health centers. Hence, strong TB quality assurances systems should be implemented in respective health facilities before practicing two spots (SS) sputum smear microscopy diagnostic approach as routine to TB laboratory diagnostic method.