Analytical variability and interpretation of results of a 3-category sperm motility assessment: 5 years’ of an Australian external quality assurance programme

Abstract

Research questionHow do laboratories perform when assessing sperm motility with a 3-category system and interpreting results as per the fifth edition of the World Health Organization manual (WHO5), and will the use of a 4-category system as per the sixth edition of the WHO manual improve their performance? DesignEighty video recordings of sperm samples were sent to over 200 laboratories spanning a 5-year period for the assessment of progressive motility. The results were reviewed relative to the all-laboratory trimmed mean (ALTM) in terms of the minimum and maximum values reported, the coefficient of variation and the proportion of laboratories indicating an abnormal result. A further 20 video recordings were sent over 1 year, with 6–11 laboratories per distribution adjusting to reporting rapid progressive motility using the 4-category system. ResultsFor the 3-category system, the videos covered a mean assessed progressive motility range of 12.0–81.1%. The mean difference between the minimum and maximum values per sample was 50.3% and the coefficients of variation were negatively correlated with the ALTM (r = –0.87, P < 0.00001). Progressive motility abnormality reporting formed a sigmoid curve, and the inflection point (50% of laboratories identifying an abnormality) gave an ALTM value of 32.01%. Preliminary results for laboratories using the 4-category system showed no performance improvement but the number of laboratories was small. ConclusionsAnalytical variation can result in laboratories crossing the clinical cut-off of the lower reference limit for samples whose motility is close to the WHO5 lower reference limit, but is less important for samples with extreme values. The benefits of a 4-category motility system are yet to be shown.