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Who 4th edition for sperm morphology

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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 Who 4th edition for sperm morphology 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.

Who 4th edition for sperm morphology

Reaching a professional consensus always involves a difficult balance of divergent views, and no consensus has been more difficult to reach than that regarding the evaluation and reporting of sperm morphology. Thus, there are sharply differing views on how to assess sperm morphology. This difficulty is reflected in the introduction Chapter 1 of the 5th edition of the World Health Organization WHO Laboratory Manual for the Examination and Processing of Human Semen 1which says, on the topic of assessment of sperm morphology, 'Some laboratories assess only normal forms, while others consider the type, location and extent of Who 4th edition for sperm morphology to be more important.

Whether these or differential or semi-quantitative assessments increase the value of the semen analysis remains contentious.

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Evidence to support the relationship between the percentage of 'normal' forms, as defined by strict categorization or computer-aided assessment of morphology with fertilization rates in vivojustifies the approach of trying to determine a morphologically distinct sub-population of spermatozoa within semen. The introduction goes on to note, 'In the 4th edition, an obvious omission, but inevitable given the lack of data, was the absence of a reference value for the percentage of morphologically normal forms; this has been rectified in this manual with the inclusion of Who 4th edition for sperm morphology on the percentage of normal forms in a fertile population.

At first impression, this lower reference limit of the percentage of normal spermatozoa in fertile men is so low that it is unlikely that a lower population from infertile men could be distinguished from it.

The aim of this article is, therefore, to discuss the usefulness of this very low reference value as well as the biological meaning of such tight categorization of a small minority of spermatozoa, and available tools and data to improve the diagnostic value of the suggested cut-off value. The interest in sperm morphology as a tool in the evaluation of a man's fertility potential started in the early s, when it became accepted that normal and pathological sperm forms could appear simultaneously in a semen sample 2.

Although the importance of Who 4th edition for sperm morphology sperm morphology has been stressed since that time—for example, with statements by Who 4th edition for sperm morphology in 3Williams and Savage in 4 and Moench and Holt in 5 that sperm morphology was the single most important source of information on the reproductive potential of spermatozoa—the manner in which the normality or abnormality of the spermatozoa should be evaluated has been controversial and remains a field of continuous debate.

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The history of sperm morphology evaluation consists of two approaches or phases, which are also reflected in the evolution of sperm morphology evaluation criteria in the consecutive WHO manuals, from the first in to the soon-to-be-published fifth edition 16789. The two approaches are the early, or liberal, approach 10 and the strict Tygerberg approach, as introduced by Menkveld in 11 and described in detail by Menkveld et al. Human males Who 4th edition for sperm morphology extreme heterogeneity, or pleomorphism, of sperm morphology among 13 and even within specific males This varied morphology contrasts with that of most domestic animals, which generally reveals a very homogeneous sperm population in individual species.

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This homogeneity for animal sperm morphology made it possible to use the appearance of the modal spermatozoon form, as seen in proven fertile animals, to describe the morphologically normal spermatozoon form for that specific Who 4th edition for sperm morphology. Owing to the heterogeneity of human sperm morphology, however, it was not possible to apply this concept successfully in human males. In the typical approach, investigators would describe different obvious abnormalities and use these abnormalities as criteria to evaluate sperm morphology.

All spermatozoa not considered abnormal, were regarded as normal, and morphologically normal spermatozoa were, therefore, identified by default. These so-called remaining normal spermatozoa as well as specific spermatozoal abnormalities were often depicted by schematic and inaccurate drawings Who 4th edition for sperm morphology liberal approach is illustrated by the words of MacLeod and Gold 16who stated, 'we are not prepared at this time to classify any but the most distorted forms as truly abnormal.

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The strict approach for sperm morphology evaluation was conceptualized in the late s and early s, as described by Menkveld in 11 and Menkveld et al. In contrast to the liberal approach, the definition for a morphologically normal spermatozoon was based on biological evidence obtained from spermatozoa found at the level of the internal cervical os. Spermatozoa found in such samples present with a mostly homogeneous appearing sperm population.

Introduction

Small biological variations in the head morphology can be observed in such samples, but these variations were considered normal. One of the most important aspects of the strict evaluation criteria is that the range allowed for these minute normal biological variations has to be kept as small as possible.

For this reason, the so-called 'borderline' or 'slightly abnormal' head forms are regarded as abnormal. By strict evaluation, the description of a morphologically normal spermatozoon is furthermore supported by the morphological appearance of spermatozoa found tightly bound to the human Who 4th edition for sperm morphology pellucida 18 There was no clear textual description for morphologically normal spermatozoa in the 1st WHO manual published in 6except in some legends for the color plates in which it is mentioned that 'the germinal cell classifications are based on those proposed by MacLeod,' thus following the liberal approach.

Although slightly improved, the 2nd WHO manual 7 followed the Who 4th edition for sperm morphology liberal approach 13 and provided only a little additional information on sperm morphology evaluation criteria.

References

In the 3rd WHO manual Who 4th edition for sperm morphologythe scheme for the morphological classification of human spermatozoa was described carefully. The manual stated, 'strict criteria should be applied when assessing the morphological normality of the spermatozoon. The 4th edition of the WHO manual 9 completely adopted the strict Tygerberg approach. Through the progression of the first four WHO manuals, some minor changes occurred in the cut-off values with respect to most semen variables, such as concentration, motility and viability.

However, for normal sperm morphology, the values were lowered dramatically from the first edition of the manual published in to the fourth edition inand now especially in the fifth edition Table 1. The first edition 6 included a table with different sperm morphology variables, such as normal, large oval heads and tapering heads, along with mean values and ranges. These values were based on the results of ejaculates from 73 men who were fathers.

(5th Edition) for the Evaluation...

The mean normal morphology was In a footnote to the table, it is stated that, 'Analysis of ejaculate multiple samples from Who 4th edition for sperm morphology least 50—70 Who 4th edition for sperm morphology of recently proven fertility, needs to be carried out at each centre to establish the normal values for a given population, in terms of sperm counts, germinal cell types and their percentages.

A note added to this value stated that, 'Although no clinical studies have been completed, experience in a number of centres suggest that the percentage of normal forms should be adjusted downwards when more strict criteria are applied. In the fifth edition of the WHO manual 1a new approach has been adopted with regard to the establishment of so-called 'normal,' or reference, values.

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This new direction is long overdue: One of the first groups to advocate these changes was that Who 4th edition for sperm morphology the Andrology Unit at Tygerberg Who 4th edition for sperm morphology, in the publications by Van Zyl et al.

As early as andVan Zyl et al. Below these normal cut-off values, two additional cut-off points could be established, one for a grey zone, in which occasional spontaneous pregnancies could still be expected, and another below which a spontaneous pregnancy could only very occasionally be expected The cut-off value for sperm morphology for the grey zone, as proposed by Van Zyl et al. These three categories are in agreement with the differentiation of semen analysis results into prognostic classes as published by Eliasson 30although he used the terms normal, doubtful, pathological and severe pathological.

Similarly, in andKruger et al. More recently, a number of papers have been published comparing sperm morphology cut-off values to in vivo pregnancy results in infertile populations or so-called fertile and subfertile populations Table 2.


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