O-285 The 6th edition of the WHO manual for the examination and processing of human semen: How should it affect our practice?
Authors: Björndahl L 
Published: June 2023

Abstract
The WHO laboratory manual (World Health Organization 2021) has widened the scope of semen examination from primarily a prognostic tool for Medically Assisted Reproduction (MAR) by indicating the importance of evaluating men with possible disorders in male reproductive functions. Practical instructions for basic examination have been clarified and focused to measures of sperm production and motility as judged from sperm number, motility (vitality if poor motility) and sperm morphology. In addition to the recommendations by the WHO, an international standard based on the same laboratory science as the WHO manual has been published (International Organization for Standardization 2021) to facilitate for laboratories to provide reliable results of semen examination.
Each ejaculate must be handled with great care before analysis begins. Time and temperature between sample collection and start of assessments is crucial. To reduce assessment variability, it is essential to ascertain that the examined aliquots are representative for the entire ejaculate and that the number of observations is sufficient to reduce the risk for significant influence of random factors. The former is handled both by aliquot volume (at least 50 µL for sperm concentration) and replicate assessment and comparison that the two assessments don’t differ too much. Regarding number of observations, 400 sperm counted in sperm concentration and in sperm motility assessments is required to reduce this source of errors to ± 10%. For assessment of sperm morphology and vitality a minimum number of observations is 200 spermatozoa.
To achieve acceptable performance, thorough in-house training is necessary. There are protocols how to set up and run such schemes (Mortimer 1994, 1994). Basic medical laboratory standards also require that the laboratory regularly performs internal quality control to monitor that inter- and intra-personal variability is under control. Each laboratory should also participate in an external scheme for quality assessment (EQA) (International Organization for Standardization 2012).
For the proper interpretation of semen examination results reference limits are important. However, the reference limits suggested by the WHO (World Health Organization 2021) come from a very mixed group of men and should therefore not be mistaken for true limits between fertility and infertility. The new WHO manual therefore argues for development of decision limits (when is it reasonable to act?) that are much more important than limits from a mixed population.
It has been argued that semen examination must be better standardized (Björndahl et al. 2016), but the compliance has been almost non-existent (Vasconcelos et al. 2022) leading to even stronger appeals for stronger improvement of basic laboratory investigations of male reproductive functions (Björndahl et al. 2022)
References
Björndahl L, Barratt CL, Mortimer D, and Jouannet P. ‘How to count sperm properly': checklist for acceptability of studies based on human semen analysis. Hum Reprod 2016: 31; 227-232.
Björndahl L, Barratt CLR, Mortimer D, Agarwal A, Aitken RJ, Alvarez JG, Aneck-Hahn N, Arver S, Baldi E, Bassas L, et al. Standards in semen examination: publishing reproducible and reliable data based on high-quality methodology. Hum Reprod 2022.
International Organization for Standardization. ISO 15189:2012 Medical Laboratories – Requirements for Quality and Competence 2012. Geneva.
International Organization for Standardization. ISO 23162:2021 Basic semen examination — Specification and test methods 2021. ISO, Geneva.
Mortimer D. Laboratory standards in routine clinical andrology. Reproductive Medicine Review 1994: 3; 97-111.
Mortimer D. Practical Laboratory Andrology 1994. Oxford University Press, Oxford.
Vasconcelos AL, Campbell MJ, Barratt CLR, and Gellatly SA. Do studies published in two leading reproduction journals between 2011 and 2020 demonstrate that they followed WHO5 recommendations for basic semen analysis? Hum Reprod 2022.
World Health Organization. WHO laboratory manual for the examination and processing of human semen. 6th edn, 2021. World Health Organization, Geneva.