Papanicolaou and Kruger assessment of sperm morphology: Thresholds and agreement

The current World Health Organization guidelines suggest that the presence of ≥ 30% normal sperm forms (i.e. PAP criteria) is consistent with normal semen quality. Critical evaluation of sperm morphology (CE; Kruger classification) has shown an excellent correlation with human in vitro fertilization. Utilizing Kruger criteria, > 14% normal sperm forms has been proposed as indicative of normal semen quality. We have performed a retrospective analysis on 261 individuals to assess the agreement between PAP and Kruger criteria for normal sperm morphology (NSM). When the threshold for NSM by PAP was set at 30%, a significant agreement was found between the percentage normal forms of both criteria (Kappa coefficient = 0.37; p < 0.001). Sixty-seven (92%) of the 73 men found to have abnormal sperm morphology by PAP had abnormal semen by Kruger classification. When the threshold for NSM by PAP was established at 50%, the Kappa coefficient was 0.48 (p < 0.001). Sixty of the 72 samples (83%) classified as normal by PAP staining were normal by Kruger criteria. Interestingly, when NSM by PAP was between 30 and 50%, the specimen was just as likely to have normal or abnormal sperm morphology by Kruger (40 vs. 60%, respectively). These results strongly suggest that a high or low percentage of NSM by PAP is in agreement with the Kruger classification. The excellent agreement of Kruger and WHO criteria at the extremes (< 30% and > 50%) may obviate the need for Kruger assessment. However, when WHO morphology is between 30 and 50%, the addition of Kruger evaluation may provide meaningful information to help better diagnose a patient and plan his treatment.