Abstract

Introduction: Current practice of examining three sputum for the diagnosis of pulmonary tuberculosis (PTB) has tended to overburden the already scarce human resources in all-purpose laboratories, and to increase the turn-around- time for patients seeking treatment. Therefore, assessing the added value of the third sputum in the diagnosis of PTB in resource-limited country with less functional External Quality Assurance (EQA) system is critical.
Materials and methods: Data on patients diagnosed with smear-positive PTB during 2012-2016 was collected retrospectively from laboratory register of nine hospitals in Eritrea. The data was extracted and analyzed for incremental yield of three sputum samples.
Results: Data from 2,484 microscopically confirmed acid-fast bacilli (AFB) smear positive PTB patients were reviewed. AFB was detected in the first sputum in 87.5% of patients, and 99.1% for the combined first and second sputum specimens. The incremental yield of the third sputum specimen as a diagnostic value was only 0.9%. No significant variation was detected by region, residence, gender or HIV.
Conclusion: The added value of the third sputum is so minimal that its omission will reduce patient visits, workload and cost for patients and health services. Therefore, even countries like Eritrea, with limited EQA, should consider limiting the number of sputum examinations to improve quality.

Keywords: Acid-fast bacilli; Incremental yield; Sputum smear microscopy; Tuberculosis