B114 Proficiency Testing As a Quality Assessment Methodology in Acid Fast Bacilli Microscopy

Abstract

Background: In 2009, The National Tuberculosis and Leprosy Control Program in Nigeria developed standardized panels for assessing laboratory proficiency in Tuberculosis (TB) smear microscopy. Laboratories supported by the Institute of Human Virology (IHV) – AIDSRelief project periodically conduct external quality assurance evaluation following this national protocol. Staff proficiency at 10 facilities was assessed in May 2012 as a measure of the quality of the IHV laboratory support model. Methodology: Each hospital received 15 slides of known, but blinded results ranging from negative to 3+ of the Acid Fast Bacilli. Laboratory personnel stained and examined the slides under their typical laboratory environment without supervision. Results were sent to the IHV Laboratory Specialist for comparison with the panel results. Results: Overall, 81% (12/22) microscopists passed scoring > 80%. Two microscopists recorded no error. Errors were detected in 31% of the 147 panel tests conducted. Low false negatives constituted 50% of the errors (23/46), where few or scanty bacilli were undetected. Others include Quantification errors (9/46; 20%) where bacilli were detected in incorrect quantities, high false negatives (6/46; 13%), where negative slides were falsely identified as highly positive (1+, 2+ and 3+), high false positives (4/46; 9%) where positive slides were falsely identified as negative and low false positives (4/46; 9%) from false identification of negative slides as scantily positive. Conclusion: These results suggest that a continuous staff competency improvement strategy through refresher trainings and standardization of AFB microscopy methodologies will be needed to have quality assured TB laboratory diagnosis.