Semen analysis with regard to sperm number, sperm morphology and functional aspects

Abstract

The new World Health Organization (WHO) Manual for Semen Analysis contains several improvements. One is that the 20 million spermatozoa per mL paradigm has been ousted in favour of proper calculations of lower reference limits for semen from men, whose partners had a time-to-pregnancy of 12 months or less. The recommendation to grade the progressive motility as described in the third and fourth editions of the WHO manual was not evidence-based, and WHO was therefore motivated to abandon it. However, the new recommendation is not evidence-based either, and it is difficult to understand the rational for the new assessment. It may have been a compromise to avoid returning to the rather robust system recommended in the first edition (1980). The unconditional recommendation of the 'Tygerberg strict criteria' is not evidence-based, and seems to be the result of an unfortunate bias in the composition of the Committee in favour of individuals known to support the 'strict criteria' method. This recommendation will have negative effects on the development of andrology as a scientific field. Given the importance of the WHO manual, it is unfortunate that the recommendations for such important variables, as motility and morphology, lack evidence-based support.

Figure 1

Cumulative probability distribution (%) of sperm concentration (million mL⁻¹) in semen from men classified as 'fertile'.

Figure 2

In this checker-shadow image, the squares A and B have exactly the same shade of grey. The brain computes a picture that makes sense in relation to its previous experiences, and the interpretation is that A is much darker than B. Reproduced from Adelson .

Figure 3

Cumulative probability distribution of spermatozoa with 'normal' morphology (%) in semen samples from men classified as 'fertile' (Eliasson and WHO manual (2010) or fertilizing one or more eggs in vitro (Morgentaler et al. ). Eliasson classified the spermatozoa after the principles presented in WHO 1980–87 (the 'traditional system'). The classification system used by WHO was the 'Tygerberg strict criteria'. Morgentaler et al. compared the two methods. The shaded areas correspond to the 95% confidence interval [CI] for data from WHO manual and Eliasson , respectively.