A methodology for establishing a diagnostic index for syndromes of unknown etiology

A method has been developed to test for heterogeneity in syndromes of unknown etiology and to distinguish between patients with and without the syndrome. The validity of the method was tested on a group of patients suspected of having a syndrome that can be diagnosed by other means (Down syndrome), and was found to be effective. The method was then applied to a group of patients suspected of having a syndrome of unknown etiology (de Lange). It was shown that the group appears to be heterogeneous. A preliminary diagnosis of having or not having the syndrome was made in about 80% of the patients.