Evaluation of structural problems in the application of strict criteria for sperm morphology assessment.

Abstract

The WHO manual for basic semen analysis and ISO 23162 describe sperm morphology assessment as a standard part of semen analysis. Older studies showed a correlation between morphology results and (artificial) conception. In more recent studies this relationship was less apparent and there is more emphasis on sperm morphology as a marker for healthy spermatogenesis (and general male health). Meantime, many laboratories ceased morphology assessment, probably due to unfamiliarity with this paradigmatic shift and to technical difficulties in the assessment, like the interpretation of morphological criteria. The aim of this study was to identify morphological criteria with high variability in results in the Dutch External Quality Control (EQC) program. Over the period 2015-2020, a total of 72 photos of sperm cells along with dichotomous propositions based on 14 criteria as defined in WHO5 (2010) were distributed in the Dutch EQC program for semen analysis. The EQC results were evaluated for variability per criterion and for trends in time. Between 2015 and 2020, 40 to 60 laboratories assessed the photos. Criteria with low variability between participants were related to acrosomal vacuoles, excessive residual cytoplasm, and tail metrics. In contrast, head ovality, regularity of head and midpiece contours, and alignment of the major axis of the midpiece and head led to the highest variability in outcomes. In general, there was a slightly positive trend (lower variability) in time, except for the criteria with the highest variability (stable or declining trend). This study indicates that there are (high) variabilities in the interpretation of the morphological criteria, leading to inconsistent outcomes of morphology assessment. The results are discussed from the perspective of imperfections in definitions and examples of the criteria as given in the WHO manuals.