A comparative study of carrier detection in haemophilia A by linear discriminant function

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Abstract
Blood samples collected from 37 definite carriers, 31 normal women and 64 possible carriers were examined for factor VIII-related activities. Five variables: factor VIII coagulant activity (VIII:C) (X1), factor VIII-related antigen (VIIIR:Ag) (X2), ristocetin co-factor (VIIIR:RC) (X3), ratio of VIIIR:Ag to VIII:C (A/C) (X4) and ratio of VIIIR:RC to VIII:C (R/C) (X5), and 28 combinations of 1-5 variables were used to derive 28 linear discriminant functions. The calculation of discriminant function coefficient, individual discriminant score and cut-off point, and the identification of normals or carriers were processed by the computer package of a biomedical computer program used at the University of California at Los Angeles, USA. A comparison of 28 linear discriminant functions for carrier detection in hemophilia A indicated that the best and simplest is y = 0.11668X1 (VIII:C) - 0.06042X2 (VIIIR:Ag), (cut-off point .hivin.y = 2.03742). It identified 94.6% of carriers without a single misclassification in the normal group, and the overall identification rate was 97.1%. Of 29 daughters of definite carriers who had no hemophilic sons, 13, or 44.8%, could be identified as carriers. VIIIR:RC was not as good as VIIIR:Ag for carrier detection; however, VIIIR:RC can be used as a supplement, if not a substitute, for VIIIR:Ag in the carrier detection of hemophilia A.