Factor VIII inhibitor assay using skin puncture blood samples

A method was developed for the measurement of factor VIII inhibitors by the Bethesda technique using small volumes of skin puncture blood. Human and porcine inhibitor concentrations on paired venous and skin puncture samples measured on 10 occasions were highly correlated, with no significant difference between them. Assays on four inhibitor negative haemophiliac patients were also negative by the skin puncture method. Sample dilution at the collection stage results in loss of sensitivity to inhibitor concentrations below 1 unit/ml, but the technique will be of value in monitoring higher concentrations when venous access is difficult and must be saved for parenteral treatment.