Abstract

We have made use of eight phenotypic findings of Down syndrome to develop an effective diagnostic index. We estimate that about 95% of patients who are suspected of having the syndrome can be categorized as having or not having it with 99.9% confidence. One can thereby make a fast clinical diagnosis on the majority of suspects before karyotyping is complete, allowing one to inform parents soon after birth and, in some instances, to make medical decisions about life-threatening defects. Furthermore, one can avoid the expense of chromosome studies on most patients who do not have the syndrome, unless there are other indications for chromosome studies. The eight features used in the index include three dermatoglyphic traits (hallucal and forefinger pattern, and palmar triradius), two measurements of physical traits (ear length and internipple distance), and three other clinical findings (Brushfield spots, wide-spaced first toe, and excess back neck skin).