Human sperm morphology assessment since 2010: experience of an Australian external quality assurance programme

Which classification criteria of sperm normality were used after the publication of the World Health Organization (WHO) 5th Edition manual (WHO5), and how did the laboratories perform?

Semen samples were sent to enrolled laboratories over a 10-year period for the determination of the proportion of spermatozoa with normal morphology. The coefficient of variation was used to indicate the level of precision between laboratories.

Before the publication of WHO5, at least six different classification criteria were in use. After 2010, WHO5 was quickly adopted, with 50% of laboratories using WHO5 criteria after the first 2 years, increasing to 94% after 10 years. Reported normal forms by WHO3 and WHO4 users remained consistent; however, the morphology results for each distribution declined significantly over time for WHO5 users (P < 0.001), suggesting laboratories were becoming stricter in their identification of normal spermatozoa. The precision of WHO5 users improved over time as shown by a steady decline in the coefficients of variation.

The introduction of WHO5 resulted in the effective adoption of its morphology classification system, with laboratories showing improved between-laboratory variation over time; however, the identification of normal forms by WHO5 users over time was inconsistent, as laboratories became stricter. Given the reduction in reported normal forms by WHO5 users, it seems that increased training of laboratory personnel or the consideration of validated objective automated analysers in the assessment of sperm morphology would seem warranted.