Comparison of methods to determine the assigned value in an external quality control programme for embryo evaluation.

This study set out to establish adequate assigned values for a National External Quality Control Programme of embryo evaluation. The results obtained by Spanish laboratories in this programme are compared with those of a group of national experts in embryo quality. Image-based embryo evaluation consists not only of classifying embryos as being of optimal, moderate or poor quality, but also of specifying the clinical decision to be taken regarding each embryo (transfer, cryopreservation or rejection). The proportion of embryos for which there was a high degree of agreement among the experts was 98.3% for embryo classification and 93.3% for clinical decision; for the laboratories, the respective values were 44.2 and 42.5%. With respect to the interobserver agreement among laboratories and experts, kappa coefficients were lower than 0.6 both for classification and for clinical decision. The experts recommended cryopreservation of a higher percentage of embryos classified as poor quality than did the laboratories (28 versus 4%, P = 0.05). The data obtained show that the agreement among laboratories is lower than among experts, and that the concordance among experts and laboratories is moderate. Therefore, it is recommended that an assigned value from external quality control programmes is established based on the consensus values obtained from experts.