A CRM-Positive variant of factor-VII deficiency and the detection of heterozygotes with the assay of factor-like antigen.

Nine patients with severe factor-VII deficiency, belonging to seven pedigrees were studied for the presence of factor-VII-CRM with an inhibitor neutralization assay. The antibody, raised in rabbits, did not precipitate the antigen and could only be used in a fluid phase assay to measure the capacity of plasma to neutralize inhibitory activity directed against factor-VII activity. In one of these nine patients normal amounts of factor-VII-CRM could be demonstrated. The CRM + patient did not show a clinical picture at variance with that of the CRM-patients. The investigation into this CRM+ pedigree revealed heterozygosity in nine out of 12 persons when using the ratio between biological factor-VII activity and factor-VII-CRM as the criterion.