What constitutes a normal seminal analysis? Semen parameters of 243 fertile men

Transcription

1 Human Reproduction vol.13 no.12 pp , 1998 What constitutes a normal seminal analysis? Semen parameters of 243 fertile men S.-E.Chia 1,3, S.K.Tay 2 and S.T.Lim 2 1 Department of Community, Occupational and Family Medicine, National University of Singapore, Lower Kent Ridge Road, Singapore and 2 Department of Obstetrics and Gynaecology, Singapore General Hospital, Republic of Singapore 3 To whom correspondence should be addressed A cross-sectional study was conducted to determine the semen parameters (i.e. volume, concentration, motility, viability and normal morphology) of proven fertile males in Singapore and compare it with the World Health Organization (WHO) recommended normal values and to examine some factors that may affect spermatogenesis. A total of 243 men, whose wives were pregnant at the time of collection of semen, provided a semen sample each after sexual abstinence for 3 days. A questionnaire was used to elicit occupational exposure, alcoholic consumption, smoking history and past significant medical history. Most subjects had normal sperm volume (56.4%), concentration (79.8%), motility (69.5%) and viability (53.5%) based on WHO criteria. However, fertile men had a low mean percentage of normal sperm morphology (20.0%), although they were normally distributed. Cigarette smoking was associated with significantly lower semen volumes even after adjusting for alcohol consumption. The sperm parameters (i.e. volume, density, motility, viability and normal morphology) were not significantly associated with ethnic differences. The WHO criterion for normal sperm morphology is too stringent, and should be adopted with caution. Normal sperm morphology is but one of many parameters for assessment of fertility. Social alcohol consumption, cigarette smoking, and recent fever did not appear to affect sperm quality in this group of fertile men. Key words: normal morphology/semen parameters/who norm Introduction The assessment of sperm morphology at the light microscope level has recently received much attention. Sperm morphology has been shown to be a significant predictor for sperm fertilizing ability in vitro (Menkveld et al., 1990; Liu and Baker, 1992). The biological endpoint in these studies was based on morphological characteristics of spermatozoa recovered from cervical mucus and/or those binding to the zona pellucida. In line with these findings, the World Health Organization (WHO) has set an empirical reference value of 30% normal forms and above as normal (WHO, 1992). However, it is not explained in either of the WHO reference guidelines (WHO, 1987, 1992) how the recommended normal values were obtained. There are other shortcomings in the WHO normal values. To quote from the manual: As for any laboratory test, it is preferable for each laboratory to determine its own normal ranges for each variable...although no clinical studies have been completed, experience in a number of centres suggests that the percentage of normal forms should be adjusted downwards when more strict criteria are applied. An empirical reference value is suggested to be 30% or more with normal forms. It is important that there should be more published reports on the range of semen analysis results from various laboratories throughout the world. These reports would enable better assessment of what the normal values are for semen parameters. A complete text search was made on the MEDLINE bibliographic database from 1989 to 1997 with the key words: normal or fertile and man or men and sperm or semen and values or result. Of the 164 papers that matched the key words, most did not report a comprehensive range of semen parameters among the fertile men. The fertile men were either sperm bank donors or volunteers who had fathered a child within the past year or more (Bielsa et al., 1994; Calvo et al., 1994). These criteria for fertility are questionable. Sperm bank donors are highly selective populations. A semen result from a man who had fathered a child within the past year is at least 1 year old. As such, it is not a good recent indicator of proven fertility. Furthermore, among those with fertile men s semen parameters, most had sample sizes of 50 men. Only one paper compared the semen parameters in a sufficiently large fertile (n 144) versus a subfertile population of 143 men (Ombelet et al., 1997). For lack of their own normal values, most human semen analysis laboratories in different countries have adopted the WHO recommended normal values for the semen analysis (WHO, 1992). However, some gynaecologists and andrologists feel that the WHO normal values are generally too stringent (Barratt et al., 1988, 1995; Check et al., 1992). It is probably for this reason that the recommended value of normal morphology of spermatozoa was decreased from 50% or more (WHO, 1987) to 30% or more (WHO, 1992). As far as can be ascertained, there is only one report on the sperm parameters of proven fertile males with sufficient large numbers to give adequate power to the study result. Ombelet et al. (1997) reported that the mean percentage of normal spermatozoa morphology was 12%, with a range of 1 27% among the 144 men whose partners were pregnant at the time of the study. Because of the lack of reference normal values, patients may be classified as having abnormal sperm function. This 3394 European Society of Human Reproduction and Embryology

2 Semen parameters of fertile men Table I. Basic characteristics of the study population Number of men 243 Mean age (SD) in years 33.2 (5.3) Alcohol intake* Teetotalers 146 (60.1) Social drinkers 97 (39.9) Smoking history No 152 (62.6) Yes 91 (37.4) Ethnic groups Chinese 139 (57.2) Malays 41 (16.9) Indians 52 (21.4) Others 11 (4.5) Mean week of pregnancy (SD) for men s wives 17.7 (SD 10.2) Values in parentheses are percentages. *Social drinkers are those who drink less than once a month, each time no more than two large bottles of beer. Figure 1. Distribution of the normal sperm morphology (%). misclassification could cause undue and unnecessary anxiety on the part of the affected patients. It might also result in unnecessary investigation or intervention for the patients and perhaps their spouses. The aims of this study were: (i) to determine the semen parameters (i.e. volume, density, motility, viability and normal morphology) of proven fertile males in Singapore and compare them with WHO normal values (WHO, 1992) and (ii) to examine some factors (i.e. past medical conditions, smoking and alcohol consumption habits) that may affect spermatogenesis. Materials and methods Study population The design of the study was cross-sectional in nature. In this study, a fertile male was defined as someone whose wife was currently (at the time of the study) pregnant but had not delivered. Females attending the antenatal clinic, at a general hospital, were approached by a female obstetric nurse. The purpose of the study was explained to the pregnant woman by the nurse. If the woman agreed to the study, she would then seek her husband s consent to participate. Only couples who had never attended an assisted reproductive programme were recruited for the study. This information was verified by both the husband and wife, separately. Each suitable male subject was given clear instructions on how to collect his semen at home, after 3 days of abstinence. He then came to the clinic on the appointed date and signed a consent form to participate in the study. Approval for the study had earlier been obtained through the relevant Hospital Ethics Committee. In addition, a questionnaire was used to elicit: (i) occupational exposure to agents that are known to affect spermatogenesis, (ii) alcoholic consumption, (iii) smoking history and (iv) past medical history. The smoking history was classified into (i) non-smoker: individuals who had never smoked a cigarette before, (ii) ex-smoker: individuals who had quit for more than a year and (iii) smoker: anyone who was currently smoking. Smokers were also asked for the duration of smoking (years) and the average numbers of cigarettes smoked per day. The couples were not asked for the length of the attempted conception interval before success. Semen collection and analysis The men were asked to collect their semen at home in the morning by masturbation into a sterile wide-mouth plastic container, after 3 days of abstinence. The samples were brought into the hospital within 1 h of collection. Time of ejaculation, abstinence period, spillage (if any), and fever during the last 3 months was recorded by the subject. All semen samples were processed and analysed by the same experienced laboratory assistant at the Fertility Clinic of the Singapore General Hospital within 1 h of receiving the samples. Volume, total sperm count, sperm viability, proportion of progressively motile spermatozoa and proportion of normal and abnormal sperm forms were examined according to the WHO guidelines for the examination of human semen (WHO, 1992). Statistical analysis Log transformation was used for sperm density to improve normality of the data. Statistical analyses were performed with standard contingency tables and tests of statistical significant (Fisher s test, Student s t-test and Duncan s test). Analysis of covariance was used to adjust for possible confounders in the data analysis. Statistical analysis was carried out using the Statistical Analysis System on the mainframe computer (SAS, 1990). Results Table I shows the basic characteristics of the study population. The men were in the younger age group (range years old). About 43% of the men did not smoke or drink alcohol at all. Most of the men s wives were in their first and second trimesters of pregnancies (range 2 39 gestation weeks). None of the subjects were on drugs or other medications at the time of the study. About 26% of the subjects gave a history of having fever at least 3 months prior to giving the semen samples. There were no significant differences in the semen parameters among Chinese, Malays, Indians and other racial groups. Most of the men had normal sperm volume (56.4%), concentration (79.8%), motility (69.5%) and viability (53.5%) based on WHO criteria (WHO, 1992). However, the men had a low mean percentage of normal sperm morphology (20.0%) (Table II). Figure 1 shows the distribution of the percentage 3395

3 S.-E.Chia, S.K.Tay and S.T.Lim Table II. Semen parameters of the men Semen parameters (n 243) Means SD Range % WHO normal Percentiles Normal value 25th 50th 75th Volume (ml) Concentration ( 10 6 /ml) 44.7* 2.8* Motility (%) Viability (%) Normal morphology (%) *Refers to geometric means and geometric SD. Based on WHO criteria (1992). of normal sperm morphology with the normal curve distribution. The majority of the fertile men s normal morphology was within 15 35%, with a median of 19%. Based on WHO normal values for the semen parameters (except normal morphology), 20.6% of the study s men would be considered as normal. However, if the WHO normal value (30%) for normal morphology was taken, 93.8% of the proven fertile males would be considered as having abnormal semen parameters. A past history of mumps and sexually transmitted diseases were the commonest medical conditions, with a prevalence of 7.8% (19/243) and 6.2% (15/243) respectively. The other past medical conditions included hypertension (2.5%), varicocele (2.1%), diabetes mellitus (2%), etc. Overall, there were no significant differences in all the semen parameters between men with a significant past medical history and men without any past medical history. However, men with a past history of sexually transmitted diseases (n 15) had significantly (P 0.001) lower mean semen volume (1.6 ml) compared to men (n 187) with no past history of sexually transmitted diseases (volume 2.4 ml). Men with past history of mumps (n 19) had significantly (P 0.001) lower percentage of normal spermatozoa compared with men who had no past medical history (n 187); 12.1 and 20.6% respectively. Smokers were found to have significantly (P ) lower volume of semen compared to non-smokers. This association is still significant even after adjusting for age and drinking history of the subjects. Drinkers had a significantly higher percentage of abnormal spermatozoa and lower semen volume when compared to the non-drinkers (Table III). However, these associations were not significant after adjusting for age and smoking habits of the subjects. There were no significant differences in any of the semen parameters between those with a history of fever 3 months prior to the semen collection and those who did not (Table III). Discussion Biological assay methods, e.g. penetration of cervical mucus (Liu and Baker, 1992) and binding to the human zona (Barratt et al., 1995), have been used as endpoints to define normal (functional) spermatozoa. These methods only assess the functional capacity of the spermatozoa and not the ability to conceive, which is the ultimate endpoint of interest with regard to fertility. Furthermore, previous studies of semen parameters were obtained from men attending infertility clinics or donors 3396 Table III. Effects of smoking, drinking and fever on semen parameters Semen Factor Sample Mean SD P-values parameters size Volume (ml) Smoking # Non-smoking Concentration Smoking * 3.1* ns ( 10 6 /ml) Non-smoking * 2.6* Motility (%) Smoking ns Non-smoking Viability (%) Smoking ns Non-smoking Normal Smoking ns morphology (%) Non-smoking Volume (ml) Drinking Non-drinking Concentration Drinking * 2.8* ns ( 10 6 /ml) Non-drinking * 2.8* Motility (%) Drinking ns Non-drinking Viability (%) Drinking ns Non-drinking Normal Drinking morphology (%) Non-drinking Volume (ml) Fever ns No fever Concentration Fever * 2.8* ns ( 10 6 /ml) No fever * 2.8* Motility (%) Fever ns No fever Viability (%) Fever ns No fever Normal Fever ns morphology (%) No fever Geometric means and SD; #P 0.01 after adjusting drinking habits. P 0.05 after adjusting for smoking habits. ns not significant. for sperm banks or a small sample of fertile men. These studies suffered either from selection bias or small sample size. As mentioned earlier, sperm bank donors are a highly selective population. In fact, one should question the rationales for using sperm bank donors to determine the normal values of semen for the male population, since they may not reflect the population s normal values. A survey was commissioned by the Human Fertilisation and Embryology Authority (HFEA) to determine the attitudes and motivations of semen donors in comparison to a matched group of non-donors. Cook and Golombok (1995) reported that, in spite of the recommendation by the HFEA that attempts should be made to recruit as semen donors older men in stable relationships who already have

4 Semen parameters of fertile men children of their own and who wish to donate for altruistic reasons, it remains the case that the large majority of men in the UK who donate semen are young single students who are largely motivated by payment. Schover et al. (1992) had also earlier reported that most of their semen donors were motivated by financial compensation. Bearing in mind all that have been cited, one should not arrive at a set of normal semen parameters based on the sperm bank donors results. Yet others (Bielsa et al., 1994; Calvo et al., 1994) have used the definition of a fertile man as one who has fathered a child in the last year or more. A semen result from a man who had fathered a child within the past year is at least 1 year old. As such, it may not be a good recent indicator of proven fertility. The present study was based on a sufficiently large group of men (243) of proven fertility (wives who are pregnant at the time of providing the semen). The findings are more likely to be an accurate reflection of sperm parameters and fertility. Ideally, it would have been better to obtain the men s semen as soon as their wives are found pregnant, but this arrangement would be logistically difficult. Thus, it would be true to say that the sperm parameter measured in the present study may not be an absolute reflection of the subjects sperm function at the time of conception. Barratt et al. (1988) examined the semen characteristics of 49 men whose partners had conceived within the last 16 weeks. A large proportion of samples (70%) when compared to the WHO standards of normality, were classified as abnormal. Similarly, based on the WHO criteria for normal values, 90% of our fertile men would have been classed abnormal. Barratt et al. (1995) studied 166 men attending an infertility clinic, whose fertility status was known. About half of the 42 fertile men (defined as pregnancy achieved within the period of the study) had less than 30% normal spermatozoa as recommended by WHO. Ombelet et al. (1997) studied the semen parameters of 144 men whose partners had recently achieved pregnancy, within 12 months of unprotected coitus. The mean and median percentage of normal sperm morphology were both 12%, with a range of 1 27%. Based on Ombelet et al. s study, none of the fertile men would have a normal sperm morphology based on the WHO criteria. In our study, we have found that 75% of the fertile men had 30% normal spermatozoa morphology. Based on the published reports, thus far, the WHO criteria for normal semen parameters would appear to be too stringent. The WHO Laboratory Manual for the Examination of Human Semen and Sperm Cervical Mucus Interaction is used, on many occasions, as a standard reference in many countries for laboratories performing basic semen assessments. The derivation of normal values should therefore be a critical exercise. Such statements in the manual (WHO, 1992), as: although no clinical studies have been completed, experience in a number of centres suggests that the percentage of normal forms should be adjusted downwards when more strict criteria are applied. An empirical reference value is suggested to be 30% or more with normal forms. should be read with caution. However, it is pertinent to note that WHO did clearly caution: as for any laboratory test, it is preferable for each laboratory to determine its own normal ranges for each variable. However, it is well known that only a few laboratories have their own normal ranges, as most men throughout the world are very reluctant to provide their spermatozoa for analysis (Whorton and Meyer 1984; Chia et al., 1996). It would be more useful if WHO criteria for normality were based on published data rather than just an empirical reference value. The WHO normal values should only serve as a guideline in the interpretation of semen results on men seeking help at the infertility clinic. Controversy still surrounds the role of sexually transmitted diseases (STD) in male infertility (Moskowitz and Mellinger, 1992). The present understanding of male infertility is limited. As such, definitive conclusions on STD and their effect on infertility cannot be fully substantiated. The study showed that men with a past history of STD (n 15) had significantly (P 0.001) lower mean semen volume (1.6 ml) compared to men with no past history of STD (n 187); 1.6 and 2.4 ml respectively. Further inferences should be done cautiously in view of the small sample size of those with a past history of STD. Similarly, men with a past history of mumps had a significantly (P 0.001) lower percentage of normal sperm morphology (12.1%) compared with men without a past history of mumps (20.1%). One of the complications of mumps is orchitis. Preveden et al. (1996) presented the results of an investigation on male fertility after mumps infection without clinical mumps orchitis. Of the 20 patients, 12 were fertile, while eight had asthenospermia. None of the 19 subjects who gave a past history of mumps recalled any accompanying episode of orchitis. It is possible that these subjects may have subclinical orchitis. There have been no reports, so far as can be ascertained, with regard to mumps orchitis and abnormal sperm morphology. The effect of smoking and spermatogenesis is a still highly debated issue, with no clear conclusion. Vine (1996) in a recent review on smoking and male reproduction concluded that although smokers as a group may not experience reduced fertility, men with marginal semen quality who wish to have children may benefit from quitting smoking. The present study s finding also showed that other than a slightly lower sperm volume there were no significant differences in all the other sperm parameters between smokers and non-smokers. However, it must be noted that more than 90% of the smokers in the present study were not heavy smokers (i.e. smoking 40 cigarettes per day). Environmental factors are suspected to be responsible, in part, for the deterioration in semen quality observed world wide during the recent few decades. Alcohol has been postulated to be a factor, considering the frequent changes in testicular function associated with heavy drinking (Pajarinen et al., 1996). Most recent studies suggest that alcohol consumption of 40 g per day is unlikely to play a pivotal role in the aetiology of poor semen quality (Dunphy et al., 1991; Goverde et al., 1995; Pajarinen et al., 1996; Vine et al., 1997). Similarly, the present study showed that there were no significant differences in any of the semen parameters between the occasional drinkers and non-drinkers. A past history of fever, within 3 months of collection of the semen sample, does not appear to be an important determinant in affecting spermatogenesis. 3397

5 S.-E.Chia, S.K.Tay and S.T.Lim In summary, the majority of the semen parameters of the 243 fertile men were within the normal values of WHO s criteria (WHO, 1992) except for the percentage of normal sperm morphology. Social alcoholic consumption, cigarette smoking, and recent fever did not appear to affect sperm quality in this group of fertile men. World Health Organization (1992) WHO Laboratory Manual for the Examination of Human Semen and Semen Cervical Mucus Interaction. Cambridge University Press, Cambridge, UK. Received on May 28, 1998; accepted on September 18, 1998 Acknowledgements This work was supported in part by the National Medical Research Council of Singapore Grant NMRC/0173/1996. References Barratt, C.L.R., Dunphy, B.C., Thomas, E.J. and Cooke, I.D. (1988) Semen characteristics of 49 fertile men. Andrologia, 20, Barratt, C.L.R., Naeeni, M., Clements, S. and Cooke, I.D. (1995) Clinical value of sperm morphology for in-vivo fertility: comparison between World Health Organization criteria of 1987 and Hum. Reprod., 10, Bielsa, M.A., Andolz, P., Gris, J.M. et al. (1994) Which semen parameters have a predictive value for pregnancy in infertile couples? Hum. Reprod., 9, Calvo, L., Dennison, L.L., Banks, S.M. and Serins, R.J. (1994). Characterisation and frequency distribution of sperm acrosome reaction among normal and fertile men. Hum. Reprod., 9, Check, J.H., Bollendorf, A., Press, M. and Blue, T. (1992) Standard sperm morphology as a predictor of male fertility potential. Arch. Androl., 28, Chia, S.E., Xu, B., Ong, C.N. et al. (1994) Effect of cadmium and cigarette smoking on human semen quality. Int. J. Fertil., 39, Cook, R. and Golombok, S. (1995) A survey of semen donation: phase II the view of the donors. Hum. Reprod., 10, Dunphy, B.C., Barratt, C.L. and Cooke, I.D. (1991) Male alcohol consumption and fecundity in couples attending an infertility clinic. Andrologia, 23, Goverde, H.J., Dekker, H.S., Janssen, H.J. et al. (1995). Semen quality and frequency of smoking and alcohol consumption an explorative study. Int. J. Fertil. Menopausal Stud., 40, Kruger, T.F., Menkeveld, R., Stander, F.S.H. et al. (1986) Sperm morphologic features as a prognostic factor in vitro fertilization. Fertil. Steril., 46, Liu, D.Y. and Baker, H.W.G. (1992) Tests of human sperm function and fertilization in vitro. Fertil. Steril., 58, Menkveld, R., Stander, F.S.H., Kotze, T.J. et al. (1990) The evaluation of morphological characteristics of human spermatozoa according to stricter criteria. Hum. Reprod., 5, Moskowitz, M.O. and Mellinger, B.C. (1992) Sexually transmitted diseases and their relation to male infertility. Urol. Clin. N. Am., 19, Ombelet, W., Bosmans, E., Janssen, M. et al. (1997) Semen parameters in a fertile versus subfertile population: a need for change in the interpretation of semen testing. Hum. Reprod., 12, Pajarinen, J., Karhunen, P.J., Savolainen, V. et al. (1996). Moderate alcohol consumption and disorders of human spermatogenesis. Alcohol Clin. Exp. Res., 20, Preveden, T., Jovanovic, J. and Ristic, D. (1996) Fertility in men after mumps infection without manifestations of orchitis. Med. Pregl., 49, SAS/STAT (1990) User s Guide, Release 6.04 edn. SAS Institute, Cary, NC. Schover, L.R., Rothmann, S.A. and Collins, R.L. (1992) The personality and motivation of semen donors: a comparison with oocyte donors. Hum. Reprod., 7, Vine, M.F. (1996) Smoking and male reproduction: a review. Int. J. Androl., 19, Vine, M.F., Setzer, R.W. Jr, Everson, R.B. and Wyrobek, A.J. (1997) Human sperm morphometry and smoking, caffeine, and alcohol consumption. Reprod. Toxicol., 11, Whorton, M.D. and Meyer, C.R. (1984) Sperm count results form 861 American chemical/agricultural workers from 14 separate studies. Fertil. Steril., 42, World Health Organization (1987) WHO Laboratory Manual for the Examination of Human Semen and Semen Cervical Mucus Interaction. Cambridge University Press, Cambridge, UK. 3398