Plasma fibrinopeptide A levels in symptomatic venous thromboembolism.

Fibrinopeptide A (FPA) was measured in the plasma of 81 patients with suspected thromboembolism. Of 47 patients with positive venography and/or lung scan, 42 had elevated FPA levels > .3 pmol/mI (mean 7.4) and 5 had levels <1.3 pmol/mI. Of 34 patients with negative venography and/or lung scan, 29 had FPA levels <1 .3 pmol/mI and 5 had levels > 1 3 pmol/ml. These results suggest limitations for the FPA assay as a sole diagnostic test for thromboembolism but indicate that the test is likely to be useful in symptomatic patients when used in addition to diagnostic methods such as venography, impedance plethysmography, and leg and lung scanning. Intravenous heparin ( mean dose 100 U/kg) lowered the FPA level into the normal range within 15 mm in 24 of 25 patients, indicating immediate suppression of thrombin action. Repeat lung scans, FPA levels, and activated partial thromboplastin times (APTT) were analyzed in 1 7 patients over the first 1 0 days of therapy. Three patients with significant new lung scan defects had elevated FPA levels on 5.2 days (mean) out of 10 and APTT < 1 .5 times the control value on 3 days out of 10. The other 14 patients with resolution or no change on the repeat lung scan had elevated FPA levels On 0.8 days out of 1 0 and APTT < 1 .5 timet the control value on 1 . 1 days out of 10. ‘Fhe present findings relating clinical thtombosis to specific cleavage of the bond between residues 16 (Arginine) and 1? (Glycine) on the Aa chain of fibrinogen provide a basis for quantitatively linking specsfic biochemical changes in the hemostatic mechanism with thrombosis.