FIBRINOPEPTIDE-A IN HUMAN-PLASMA - EVALUATION OF A NEW RADIOIMMUNOASSAY TECHNIQUE ON MICROLITER-PLATES

Fibrinopeptide A has been measured in plasma of healthy persons and patients with liver-cirrhosis or venous thrombosis. Three steps of the radioimmunoassay as described by NOSSEL were modified: 1) elimination of plasma dialysis; 2) performance on microliter-plates; 3) double antibody method. All modifications were compared to the original method. The detection limit of the modified method was 0.16 ng/ml plasma. The within assay" coefficient of variation was estimated 10.6% for low and 7.2% for high concentrations. Added amounts of fibrinopeptide A were recovered from 70% to 100%. "Inter assay" coefficient of variation was 9.5%. In normal plasma a mean concentration of 1.8 ng fibrinopeptide A /ml plasma was measured (range 0.16 ng/ml - 2.2 ng/ml). In patients with liver-cirrhosis fibrinopeptide A was elevated in plasma (mean: 27.3 ng/ml; range 2.7 ng/ml - 156 ng/ml). High fibrinopeptide A immunoreactivity in patients with venous thrombosis declined at a rate equivalent to a half-life of 2 minutes after intravenous injection of heparin. The radioimmunoassay technique on microliterplates is about 6 - 8 fold less time consuming than previously described methods. © 1979."