Quality Assurance of Malaria Microscopy in Mali

The Improving Malaria Diagnostics (IMaD) project assessed the sensitivity, specificity and agreement of microscopists and their supervisors against Mali’s national referral laboratory, INRSP as gold standard. Low agreement between microscopists and gold standard was mainly due to low specificity, the former may be reporting stain precipitate and other artifacts as malaria parasites. Supervisors help identify what improvements they can introduce (i.e. filtering Giemsa stain) to reduce false positives. As a group, laboratory supervisors need to improve their sensitivity, while as a group microscopists must improve both their specificity and sensitivity. In the Venn diagram, the black square represents at scale the total number of slides used for external quality assurance, the blue circle represents slides reported as positive by INRSP, the red circle represents slides reported as positive by laboratory supervisors re-reading slides, and the green circle corresponds to slides reported as positive by microscopists. Eighty percent of false positives for supervisors overlapped the lab staff’s false positives, suggestive that some supervisors may not have been blind to staff results, which influenced their reports.