Multicenter proficiency study for detection of Toxoplasma gondii in amniotic fluid by nucleic acid amplification methods

A proficiency panel was designed to assess the performance of nucleic acid amplification technologies for the detection of Toxoplasma gondii in amniotic fluid.MethodsThe proficiency panel consisted of five lyophilised coded samples in a range of concentration between 5 to 1000 parasites/ml and a negative control. The distribution also included a questionnaire on the applied methods.ResultsThirty-three laboratories in 17 countries participated and returned a total of 38 data sets. The percentage of data sets achieving correct results on all panel samples was 42.1%, whereas two or more incorrect or equivocal results were reported for 36.8%. The lowest concentration (5 parasites/ml) was not identified correctly in 15 (39.5%) data sets. False positive results were reported by two laboratories both of which had not included a step in their procedure to rule out contamination. In 32 (84.2%) data sets an “in-house” method was used, and in 6 (15.8%) sets a commercial assay was applied.ConclusionsOverall, the results of this study demonstrate the need for improvements in both sensitivity and specificity of molecular detection methods of T. gondii and for the development of international reference materials to help laboratories with the development and validation of their assays.