Diagnosis of protein C deficiency in patients on oral anticoagulant treatment: comparison of three different functional protein C assays.
The efficacy of three different protein C activity assays and of protein C antigen determination for the diagnosis of protein C deficiency was studied in 13 protein C deficient patients (11 with type I, 2 with type II deficiency) and in 51 presumably non-deficient patients (control group), both groups being on oral anticoagulant (OAC) treatment. For protein C activity measurement (1) the assay according to Francis (slightly modified) with thrombin activation and measurement of activated protein C in the aPTT system, (2) an assay using Protac activation and chromogenic substrate (Protac-CS) and (3) an assay using Protac activation and the aPTT system (Protac-PTT) were used. Protein C antigen was determined by Laurell immunoelectrophoresis. The three activity assays gave different results, with the highest values obtained by the Protac-CS assay and the lowest values by the Protac-PTT assay. The Francis assay gave intermediate results. Protein C activity and antigen values were significantly lower in protein C deficient patients compared to the control group. Protein C activity tests had a higher discriminative power than the antigen determination. After taking into account the intensity of treatment, by the Francis assay all deficient and non-deficient patients were correctly classified, by the Protac-CS and the Protac-PTT assay 2 and 4 patients, respectively, were misclassified and by the antigen assay 8 patients were misclassified. Calculation of the ratios of protein C activity to factor II activity was of high discriminative power. We conclude that for diagnosis of protein C deficiency protein C activity tests are superior to antigen determination not only in type II but also in type I deficient patients.(ABSTRACT TRUNCATED AT 250 WORDS)
I. Department of Internal Medicine, University of Vienna, Austria.
I
I
Pabinger
P A
PA
Kyrle
W
W
Speiser
U
U
Stoffels
M
M
Jung
K
K
Lechner
D015110:4-Hydroxycoumarins / Q000627:therapeutic use*; D000284:Administration, Oral; D006801:Humans; D007122:Immunoelectrophoresis; D010644:Phenprocoumon / Q000627:therapeutic use*; D011237:Predictive Value of Tests; D011486:Protein C / Q000378:metabolism; D020151:Protein C Deficiency; D013927:Thrombosis / Q000097:blood / Q000188:drug therapy / Q000235:genetics*
D015110:4-Hydroxycoumarins; D011486:Protein C; D010644:Phenprocoumon