Carrier detection in haemophilia A families. Comparison of conventional coagulation parameters with DNA polymorphism analysis: First report from India

Linear discriminants that include data on factor VIII:C and von Willebrand factor antigen levels are well-established tools in estimating the probability of carriership in haemophilia A families. A comparison between the conventional coagulation data, i.e. the ratio of factor VIII:C and von Willebrand factor antigen, and the DNA analysis techniques was made in 98 confirmed carriers (39 obligatory, 69 detected by gene tracking analysis) and 71 normal age matched females who did not have any history of bleeding and were not taking any drug. The lowest misclassification rate, i.e. 7% among the carriers, was seen when a cut-off value of 0.7 was chosen. In the case of normals, all were outside this cut-off value. Thus, it was considered as a workable reference value for classifying the carriers in haemophilia A families in our laboratory. We conclude that the optimal service for haemophilia A carrier diagnosis must include above coagulation test probabilities as well as DNA marker studies. However, it is recommended that the smaller laboratories in developing countries can benefit immensely by only establishing factor VIII:C and von Willebrand factor antigen estimation.