For appreciable ethnic differences in false positive rates, use different cut off points

Abstract

EDITOR,—Lucy Gilbert and colleagues report ethnic differences in biochemical screening for Down's syndrome and the relative ineffectiveness of the programme in Indian Asians.1 At national meetings of the Association of Clinical Biochemists we presented our findings on the ethnic differences in maternal serum (alpha) fetoprotein and free β human chorionic gonadotrophin concentrations2 and the differences in false positive rates in the various groups, which remain unchanged even after the use of “ethnospecific” medians.3 The false positive rate …