Detection of Hemophilia a Carriers by Repeated Factor VIII Activity/Antigen Determinations

Detection of hemophilia A carriers (C), using factor VIII (fVIII) activity (Ac) and antigenicity (Ag) measurements, has been hampered by an overlap of results obtained in normal females (NF) and obligatory carriers (OC). In an attempt to improve the specificity and sensitivity of C detection, 29 OC and 33 NF were examined 3 times. FVIII Ac and fVIII Ag were determined in fresh plasma samples, employing a one stage method and the Laurell technic with rabbit anti fVIII antiserum, respectively. Using the mean of the 3 pairs of measurements, a discriminant function, based on Bayes’ theorem, was obtained for calculating the probability that a woman is a C. Three ranges of measurements were defined: Definite C, possible C and definite NF. The results were as follows:

If only the first pair of measurements was used, the results were much less satisfactory:

Thus, for each suspected C, the relative odds of being a C can be assigned by using this function, but the results should be based on the mean of 3 measurements.

 

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