CHAPTER 2 Standard procedures 101
2.17.4 Assessment of abnormal sperm morphology Categorizing all abnormal forms of spermatozoa may be of diagnostic or research beneďŹ t. If desired, note the nature of the defects and calculate the percentage of spermatozoa with defects of the head (%H), midpiece (%M) or principal piece (%P), and those with excess residual cytoplasm (%C). A multi-key counter can be used, with one key for normal, one for abnormal, and one for each of the four abnormal categories (H, M, P, C). Such a counter allows each spermatozoon to be counted only once, and each of its abnormalities to be scored separately.
y From the final assessment of 400 spermatozoa, it is possible to obtain the percentage of normal and abnormal spermatozoa (the two figures should add up to 100%), as well as the percentage with each type of abnormality, i.e. %H, %M, %P and %C (these figures will not add up to 100%).
y The percentage of spermatozoa in these abnormality classes is obtained by dividing the total number of abnormal spermatozoa with a specific defect by the total number of normal and abnormal spermatozoa scored Ă—100. These numbers can also be used to calculate multiple anomalies indices (see Section 3.1). 2.17.5 Worked example Example. Of 200 spermatozoa scored with a six-key counter for replicate 1, 42 spermatozoa are scored as normal and 158 as abnormal. Of the 158 abnormal spermatozoa, 140 have head defects, 102 have midpiece defects, 30 have principal piece defects, and 44 have excess residual cytoplasm. Results from replicate 2 are 36 normal and 164 abnormal spermatozoa, of which 122 have head defects, 108 midpiece defects, 22 principal piece defects, and 36 excess residual cytoplasm. Only the normal category is compared for acceptability of replicates. Replicate 1 has 21% normal sperm and replicate 2 has 18%. The mean of these values is 19.5% (rounded up to 20%), and the difference 3%. From Table 2.1, it is seen that, for an average of 20%, a difference of up to 8% would be expected to occur by chance alone. As the observed difference is less than this, the results are accepted and the mean values reported: normal forms (42 + 36)/400 = 20%, abnormal heads (140 + 122)/400 = 66%, abnormal midpieces (102 + 108)/400 = 53%, abnormal principal pieces (30 + 22)/400 = 13%, and percentage with excess residual cytyoplasm (44 + 36)/400 = 20%. Note: These categories do not add up to 100% since each abnormality is tallied separately and some spermatozoa have multiple defects. Comment: A more detailed analysis of abnormal spermatozoa, with various indices combining the number of abnormalities in each region per abnormal spermatozoon, is given in Section 3.1.1.