Reference limits: limited references in laboratories worldwide

Abstract

The newly revised World Health Organization (WHO) semen analysis manual provides the lower refe rence limits of semen parameters based on "the raw data from between about 400 and 1 900 semen samples, from recent fathers in eight countries on three continents": Australia, Europe and North America [1]. The other continents, Asia, Africa, and South America, and most regions of the above three continents, such as southern Europe, were not represented in the raw data used to generate the reference limits. To my knowledge, no valid and well-controlled data regarding semen from men whose partners had conceived within the preceding 12 months have been collected from these unrepresented regions. Profound comments on this regard have been made and published in the Special Issue in Asian Journal of Andrology on "Semen analysis in 21st Century Medicine" in Issue 1 in 2010 [2][3][4][5]. In this letter, I would like to present some of my views and suggestions on reference limits of semen parameters.Previous data from screened and general populations showed that there are obvious differences in semen quality between continents [6], countries [7] and even different areas in the same country [6,8,9]. Some of the studies also revealed temporal differences [10]. The underlying reasons were unclear. Temporal and geographical differences in semen quality might reflect differences in environmental factors and, ethnic or genetic backgrounds or a combination of factors. Although more studies are needed to understand the full biological significance of these differences, a study by Joffe et al. [11] suggested that they might be related to differences in fecundity. The observation that spermatogenesis in Asian men appears to be more susceptible to suppression by steroidal contraceptives than that in Caucasian men has been proposed to be related to ethnic differences in testicular structure (smaller testes, reduced number and function of Sertoli cells and reduced daily sperm production) and spermatogenic potential [12]. Differences in reproductive endocrinology between Asian men and Caucasian men have also been suggested [13]. It is possible that more sperm are produced in individuals in some ethnic populations, resulting in higher fecundity. Even in cases of similar levels of sperm production, it is possible that higher fecundity can be achieved by sperm that are better able to fertilise the egg or, conversely, by eggs that are easier to be fertilized. As a result, the fifth centiles (with 95% confidence intervals) from the raw data derived from a population with higher sperm production might be higher. These values would be lower in a population with sperm or eggs that result in higher fecundity. Therefore, it seems highly reasonable to suppose that the reference limits in men whose partners were pregnant within the last 12 months vary among countries with different ethnic backgrounds. Great caution should be taken when using the WHO manual's reference limits

Semen parameters in fertile US men: the Study for Future Families

“…Povey et al (2012) reported that Black ethnicity was a risk factor for low motile sperm concentration in a case-control study of male partners of infertile couples. Huang, 2010 noted that current WHO reference ranges are based on men living in Australia, Europe and North America and that data on semen parameters in fertile men living outside these continents are lacking and that the possibility of ethnic differences should be considered in establishing reference ranges. As the number of Black men in our study was relatively small compared with White or Hispanic/Latino men, these results should be viewed as preliminary, but worthy of further study.…”

Basic Phenotyping of Male Fertility from 2019 to 2020 at the Human Sperm Bank of Fudan University

“…Semen quality has received attention from different professional disciplines. Since a decline in male semen quality was first reported in the 1990s, countries, regions and ethnic groups have continued to pay attention to changes in male semen parameters in their own populations (Elbardisi et al 2018;Glazer et al 2019;Huang 2010;Redmon et al 2013). Although the findings have been inconsistent from time period to time period and from region to region, the focus on semen parameters has not diminished.…”