Summary
Previously, assays of fibrin-fibrinogen degradation products (FDP) had to be performed
on serum samples. However, monoclonal antibodies (Mabs) are now available which permit
the measurement of FDP directly in plasma. We have employed two Mabs, one monospecific
for FDP originating from crosslinked fibrin and another panspecific for the FDP fraction,
to determine normal FDP levels in plasma and serum. The monospecific Mab gave a value
of 40 ng FDP/ml in plasma and 10 ng/ml in serum, while the serum level of FDP recorded
using the panspecific Mab was >1000 ng/ml, at all the concentrations of thrombin employed.
Similarly, when a solution of purified fibrinogen was treated with thrombin, the concentration
of FDP present in the clot supernatant was >1000 ng/ml when assayed using the panspecific
Mab. Thus during serum preparation as much as 75% of the native FDP is incorporated
into the clot while in excess of 1000 ng/ml of laboratory generated FDP, probably
incompletely polymerized fibrin, is measured using panspecific antisera. These data
indicate that current FDP assays using polyclonal antibodies are not a reliable reflection
of the FDP level generated in vivo. The use of FDP-specific Mabs which do not react
with fibrinogen is recommended for future FDP assays performed directly on plasma.
Keywords
Fibrin degradation products - Monoclonal antibodies
