Carrier Detection in Classic Hemophilia by Combined Measurement of Immunologic (VIII AGN) and Procoagulant (VIII AHF) Activities

Abstract

Accurate carrier detection in classic hemophilia has been difficult because of (1) technical problems related to the performance of both immunologic (VIII AGN) and procoagulant (VIII AHF) determinations, and (2) statistical problems related to the analysis of these data. VIII AHF was determined by a one-stage assay based on the partial thromboplastin time (PTT). VIII AGN was measured by the method of quantitative Immunoelectrophoresis. The discriminant function U. = 0.67 In (AHF) – 3.17 AGN × 10^–3 was calculated for a validation group of 20 normal persons and for seven obligate carriers, and tested for accuracy of prediction on a cross-validation group of seven additional normal women and ten additional obligate carriers. A U. score of ≥2.54 correctly identified 25 of 27 normal persons. Sixteen of 17 obligate carriers had U. scores below 2.54. In addition, of seven possible carriers, four were identified as normal and three as carriers. Five normal women taking oral contraceptives had disproportionately high U. scores. It is concluded that detection of carriers of classic hemophilia should be possible in the clinical laboratory by calculation of a discriminant function from combined measurements of VIII AGN and VIII AHF.