Clinical significance of the low normal sperm morphology value as proposed in the fifth edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen

Abstract

The very low cut-off value for sperm morphology of 4% morphologically normal spermatozoa, as proposed in the new edition of the World Health Organization (WHO) manual on semen analysis, is in agreement with recently published values and reflects the trend of a decline in reported mean values for normal sperm morphology. The reduced value for morphologically normal spermatozoa over the years may be due to several factors. The first is the introduction of strict criteria for the evaluation of sperm morphology. Other reasons may include the introduction of additional criteria for sperm morphology abnormalities and the suggested decrease in semen parameters because of increasing negative environmental influences. Although on its own the newly proposed very low normal value may not provide the strong predictive value for a males' fertility potential, as originally reported for sperm morphology evaluated according to strict criteria, a good predictive value can still be obtained if the holistic, strict approach for sperm morphology evaluation is followed together with additional sperm morphology parameters now available, because certain morphology patterns and sperm abnormalities are now known to be of strong prognostic value. In addition, better international standardization of the technical methodology, consensus on the interpretation of sperm morphology evaluation criteria and standardized international external quality control (EQC) schemes, are of utmost importance to maintain the good predictive value of sperm morphology.

Double-blind prospective study comparing two automated sperm analyzers versus manual semen assessment

“…The significant differences in morphology are seen in the normozoospermic group only, though the medians of the data reported by all three methods are well above the 4 % reference value cut-off. These differences are quite minor when considering that the assessment of this parameter is highly variable due to the complexity and subjectivity of manual morphology and the WHO 5th normal morphology cut-off of 4 % [24]. Low normal morphology median values coupled with the low precision of the manual and CASA assessment (95 % confidence intervals are: Manual 3.7 and CASA 3.8 vs. SQA-V GOLD 1.5) resulted in the significant differences that were reported.…”

Dimensions of human ejaculated spermatozoa in Papanicolaou-stained seminal and swim-up smears obtained from the Integrated Semen Analysis System (ISAS®)

“…The lower panel depicts frequency histograms of the morphometric data from spermatozoa selected as being 'normal' in semen or swim-up samples. 'smooth', 'irregular' and 'asymmetric' is extremely subjective [1,2]. Our technicians' impression has been that semen samples from diffe rent men contain spermatozoa of different size.…”

“…These had the characteristics described by the Tygerberg criteria [1] of smooth oval outlines, not too round or long, no more than two vacuoles in the acrosome region covering no more than 20% of the head area and no vacuoles in the post-acrosomal area with insertion of the midpiece along the long axis of the head. To eliminate betweenobserver bias, only one observer (conversant with the criteria of the form of sperm head cell considered 'normal' in the new WHO manual [3]) selected these cells from the monochrome images.…”

“…The assessment of sperm morphology remains a controversial topic: should purely 'normal/ideal' forms be assessed; how should normal forms be defined [1,2]; should abnormal forms be monitored; should multiple 872 npg anomalies' indices be calculated? Previous editions of the World Health Organization (WHO) handbook for semen analysis [3][4][5] recommended assessing 'normal' (or 'ideal') forms, as being representative of potentially fertilizing spermatozoa.…”

“…However, subjective analysis by technicians may be influenced by the appearance of other spermatozoa in the sample; for example, a 'normal' spermatozoon in one semen sample containing other spermatozoa of larger size may be considered to be abnormally small and not counted as normal, whereas in another sample a similar spermatozoon, with smaller neighbouring spermatozoa, may be discounted as abnormally large. Although this can be checked by ocular measurements of sperm head size, it emphasizes the importance of accurate sperm head measurements [1].…”