The term ''D-dimer assay'' suggests, that these assays report the conc
entrations of the end-stage degradation product of crosslinked fibrin.
This hardly occurs in patients. Degradation products of cross linked
fibrin rather occur with a wide range of molecular weights, and compri
se various numbers of the D-dimer motif. Moreover, the numerical value
s obtained with different ''D-dimer'' assays vary widely. The variatio
ns are probably due to differences in reactivity of the various monocl
onal antibodies used with the various D-dimer containing degradation p
roducts as they occur in patients; and to the various calibrators with
a value assigned by the manufacturers. For the reasons indicated abov
e a calibrator in the strict sense (e.g. pure D-dimer) is not feasible
. This study shows that: it appears feasible to generate a conversion
factor for each of the ''D-dimer'' assays studied? which will make the
widely varying results obtained with these kits comparable; that the
conversion factors can be based on a pool of real patient samples; and
that the conversion factors are pool-independent. The next and final
step in this study is to prepare and make available an international r
eference material for use by manufacturers and others facing a compari
son problem. This is being carried out, in collaboration with the NIBS
C (Dr. P. Gaffney), and the material is expected to, be available in e
arly 1997.