Assessing the efficacy of The American Fertility Society's classification of endometriosis: application of a dose-response methodology

In order to promote uniform reporting of endometriosis. The Americal Fertility Society (AFS) recently proposed a classification in which severity was categorized on the basis of both location and extent of disease. The results of this study indicate that the AFS scale poorly specifies the relation between severity of disease and pregnancy outcome after therapy, because of the arbitrary point scores assigned to each classification category, and the arbitrary cutoff points chosen to divide patients into severity groupings. A nonparametric monotonic estimator, which generates a dose-response relationship between AFS score (dose) and pregnancy following treatment (response) is shown to improve the discriminatory power of the AFS scale; however, in order to obtain the full benefit of the detail provided by the AFS classification, it is recommended that the current arbitrary individual-category weights be replaced by empirically derived weights.