Summary
Amidolytic assay of antithrombin III on capillary blood can validly substitute for
similar assays performed on venous blood, as an excellent correlation exists (r =
0.95).
For the amidolytic assays of heparin cofactor activity, a much less satisfactory correlation
is found (r = 0.81). Results are far more dispersed and a decrease is observed in
late capillary samples.
Using a low heparin concentration to assay heparin cofactor activity leads to surprisingly
high activities for capillary blood. The same type of discrepancy is observed during
the earliest stages of clotting of venous blood.
Keywords
Antithrombin - Chromogenic substrates - Capillary blood - Early blood clotting