External Quality Assurance Assessment of Smear Microscopy for Tubercle Bacilli by Blind Rechecking of Slides

Abstract

This study aimed to assessment of smear microscopy in net work of tuberculosis bacilli by blind rechecking of slides. A total of 288 positive (48) and negative (240) sputum smears were collected from peripheral TB laboratories located in four States ( Sinnar, Baher Aljabel, Red Sea, and Blue Nile) using Lot Quality Assurance Sampling technique. The selected slides had been sampled from the slides of the fourth quarter of the year 2005. All slides were checked microscopically at peripheral then re-checked in state level, as first controller, blindly without knowing their previous examination results. Then the smears were cleaned with xylene before being read by the second controller. Most of errors are found in the peripheral stage were as follow HFP are more frequently in Red Sea 6%, while it was low in Bahar El-Jabal 0.1% and HFN more frequently in Blue Nile 3% while it was zero in Bahar El-jabal. LFN and LFP are higher in Red Sea 1.5% while it was zero in Blue Nile and Sinnar state. Quantification errors are found higher in Red Sea 1.5% while they were zero in Sinnar State. The study concluded the important of the quality control, also the implementation of blind rechecking method. for broad action of assessing and following of smear microscopy, Re-staining helped in resolving problems of the false positive and negative which it is due to insufficient decolrization. Also deposition of stain and preparation of smear and staining process, also take time in reading and following the WHO instructions in quantity reading to avoid quantification errors. Also the exact picking of part for smear to avoid thickness and make smear three/four of slide ,avoid heating during fixation.