COMPARISON OF THE REPRODUCIBILITY OF THE WHO CLASSIFICATIONS OF 1975 AND 1994 OF ENDOMETRIAL HYPERPLASIA

In a blinded, randomized design, six histopathologists with an interes t in gynecological pathology examined the inter- and intraobserver var iation of the histopathological diagnosis of endometrial hyperplasia a ccording to the World Health Organization (WHO) classification of 1975 and the new WHO classification of 1994. On four occasions, the pathol ogists assessed hematoxylin/eosin-stained slides from 128 cases origin ally diagnosed and coded in the Snomed system as endometrial hyperplas ia. In the first and third rounds, the slides were classified accordin g to the 1975 classification and in the second and fourth rounds accor ding to the 1994 classification. The overall interobserver agreement i n the two rounds where the 1975 classification was used was 0.47 and 0 .51, and the kappa values 0.24 [95% confidence interval (CI) 0.21-0.27 ] and 0.30 (95% CI 0.27-0.33). The overall interobserver agreement in the two rounds using the 1994 classification was 0.45 and 0.41 and the kappa values 0.25 (95% CI 0.23-0.28) and 0.20 (95% CI 0.17-0.22). Red ucing the classification to two categories with clinical significance (atypical endometrial hyperplasia versus others in the 1975 classifica tion, and atypical endometrial hyperplasia, complex versus others in t he 1994 classification) increased the overall agreement of the 1975 cl assification in both rounds to 0.91 and of the 1994 classification to 0.92 and 0.90. The kappa values increased to 0.54 (95% CI 0.49-0.58) a nd 0.49 (95% CI 0.45-0.54) in the 1975 classification and to 0.59 (95% CI 0.54-0.63) and 0.42 (95% CI 0.37-0.46) in the 1994 classification. The intraobserver overall agreement for the 1975 classification range d from 0.80 to 0.55 and the kappa values from 0.70 (95% CI 0.58-0.81) to 0.28 (95% CI 0.17-0.39). The intraobserver overall agreement for th e 1994 classification ranged from 0.71 to 0.46 and the kappa values fr om 0.60 (95% CI 0.51-0.70) to 0.20 (95% CI 0.09-0.30). It is concluded that there is considerable inter- and intraobserver variation using b oth the 1975 and the 1994 classifications of endometrial hyperplasia. We propose that there is need for a specification and for a simplifica tion of the classification.