We studied activated protein C sensitivity ratio (APC-SR), factors V and VIII activity and von Willebrand antigen in control women, women using oral contraceptives, and pregnant women at delivery. The mean APC-SR of 2.4 in pregnant women was significantly lower than the mean APC-SR value of 3.5 for both the other groups and 45% of pregnant women had a ratio below the 5th percentile of the control group. None of them carried the R506-->Q mutation. This decreased ratio at delivery appeared to be connected, at least in part, with increased VIII activity. Thus, APC-SR at delivery should not be used to detect APC resistance.

No abstract

Factor XI (FXI) deficiency is an inherited autosomal recessive disorder associated with bleeding of variable severity. However, many cases of dominant disease transmission have been recently described. This disorder is rare in the general population, whereas it is commonly found in individuals of Ashkenazi Jewish ancestry. This study reports the molecular genetic analysis of FXI deficiencies in 11 unrelated families of different origin. Five novel mutations have been identified. Severe FXI deficiency of two unrelated patients resulted from two novel mutations: one deletion (960-961delGT) in exon 9 predicting a frameshift, and a Ser-4Leu mutation located in the signal peptide. In addition, three novel missense mutations associated with partial FXI deficiency have been identified: Cys122Tyr, Glu297Lys and Glu579Lys.

Activated protein C resistance ratio (APC-Rr), factor VIIIC (FVIIIC) and plasma fibrinogen levels were studied in patients with inflammatory disease. The patient mean APC-Rr was significantly lower than in the control group. This decreased ratio in inflammatory diseases appeared to be connected with increased FVIIIC. Moreover, supplementation of plasmas with purified factor VIII decreased the APC-Rr in plasma from both groups, and suppressed the difference between groups. These data suggest that factor VIIIa and factor Va compete for protein C-catalysed cleavage. Ratios were identical in both groups when FVIIIC level was lowered by dilution in factor V deficient plasma.