Quality assessment of Sputum-Smear Microscopy performed by the Tuberculosis Laboratory Network of the Metropolitan Region of Baixada Santista/SP

Abstract

The Brazilian Ministry of Health national program for tuberculosis (TB) control (Programa Nacional de Controle da Tuberculose) determines the sputum smear microscopy as the standard methodology for TB diagnosis. In order to achieve diagnosis quality assurance it is recommended to set up an External Quality Assessment (EQA) scheme in the TB diagnosis laboratory network. This study aimed at evaluating the quality of sputum smear microscopy performed by the local laboratory network of the metropolitan area of Baixada Santista, SP, by means of an indirect supervision. The 5,691 sputum samples stained with Ziehl-Neelsen in nine local laboratories were evaluated. The applied EQA methodology was in accordance with the National TB and Other AFB Laboratory Surveillance Manual – Ministry of Health, 2008. The analyzed parameters were: macroscopic (smear uniformity) and microscopic (staining) analyses of the sputum smears and bacilloscopic index (C%). Of 713 analyzed slides, 529 (74.2 %) were satisfactory on macroscopic features and 631 (88.5 %) on microscopic evaluation. In the slides rechecking, one laboratory showed two false-positive results and C =97.5 %. Although the general results have been acceptable, a continuous EQA activity should be carried out, emphasizing the use of correcting actions on the common sources of error that may occur in performing the AFB microscopy technique.