Analysis of the performance of external quality assurance of tuberculosis sputum smear microscopy at medical institutions in Chaoyang district, Beijing

Objectiveassess the performance of quality control of the acid-fast bacillus (AFB) microscopic examination of tuberculosis (TB) sputum smears at the tuberculosis laboratories of twelve comprehensive hospitals above the second grade and twelve tuberculosis control centers in Chaoyang District, Beijing. MethodsField evaluation and blind rechecking was performed at the tuberculosis laboratories according to the External Quality Assurance for Sputum Smear Microscopy (EQA) of Chinese Tuberculosis Prevention and Control Plan. ResultsA total of 1671 sputum smears were subject to blind re-checking from 2006 to 2008, resulting in a qualitative consistency of 95.2% and a positive quantitative consistency of 70.2%. The qualitative consistency at comprehensive hospitals was 95.6%, and positive quantitative consistency 64.9%; the qualitative consistency at tuberculosis control centers was 94.7%, and positive quantitative consistency 75.0%. Quality indexes for sputum smears, the qualification rates of sputum cell counts, size, thickness, stain and shed cells, were 93.4%, 66.1%, 75.4%, 91.0% and 97.1%, respectively. Field evaluation revealed a superiority in the laboratory areas and equipments at tuberculosis control centers, featuring stable sputum-smear examiners who had received appropriate pre-post training, over comprehensive hospitals, despite stronger educational background and professional titles of the technicians in these hospitals. The detection rate of positive patients was higher at tuberculosis control centers than that in comprehensive hospitals. ConclusionEQA blind rechecking and field evaluation are effective approaches in improving the quality of AFB sputum-smear microscopy. Further improvement is desired in the performance of AFB microscopy at medical institutions of different levels.