External quality assessment by European mycobacterial laboratories: results of AFB microscopy and identification rounds

We analyzed mycobacterial stain, culture and identification EQA data from altogether 134 laboratories in 15 mainly European countries over a 4-year period. The aim was to get an overview of the performance and methods and identify diagnostic challenges. The overall success rates for staining and identification were 94% and 91%. The false negative rate for staining was significantly higher for the medium positive than the strong positive slides (11% vs 4%). The false positive rate on negative slides was 10%, indicating contamina-tion issues. The overall success of M. tuberculosis detection was high with error rates ranging from 0.7% to 1.2%. Pre-or postanalytical errors accounted for most of the unsuccessful responses. The detection of nontu-berculous mycobacteria (NTM) was less consistent; accurate species identification depended on the assays used. Only 19% of participants performed species level identification for NTMs, 47% detected the presence NTMs while 21% focused on ruling out TB. (c) 2022 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)