PLASMA THROMBOPLASTIN ANTECEDENT (PTA, FACTOR-XI) - SPECIFIC AND SENSITIVE RADIOIMMUNOASSAY

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 50  (3) , 377-385
Abstract
A specific, sensitive, and reproducible radioimmunoassay for human plasma thromboplastin antecedent (PTA, factor XI) was developed with purified PTA and monospecific rabbit antiserum. Precise measurements of PTA antigen were possible for concentrations as low as 0.3% of that in normal pooled plasma. Normal plasma contained approximately 6 .mu.g PTA/ml. A good correlation (correlation coefficient 0.68) existed between the PTA procoagulant assays and radioimmunoassays among 50 normal adults (25 males and 25 females). PTA antigen was markedly reduced in plasma of 13 patients with congenital homozygous PTA deficiency (range < 0.003-0.128 U/ml) and 9 patients with hepatic cirrhosis (0.35 .+-. 0.17 U/ml), but was normal in those of 9 patients under treatment with warfarin, 8 patients with disseminated intravascular coagulation and 16 patients with other congenital clotting factor abnormalities, including prekallikrein deficiency (Fletcher trait) and high MW kininogen deficiency (Fitzgerald trait).