A proposed stoichiometrical calibration procedure to achieve transferability of D-dimer measurements and to characterize the performance of different methods.
BACKGROUND
There is little transferability between D-dimer levels obtained by different reagents today. This makes it difficult to compare results from different clinical studies.


OBJECTIVE
We give a comprehensive proposal for calibration of D-dimer assays. All crucial steps and underlying assumptions are made explicit.


METHODS
The new approach is based on using a set of fibrinolysates of patient samples clotted and treated with tPA to obtain maximal conversion to D-dimers. Their expected maximal D-dimer concentrations are calculated stoichiometrically from their different fibrinogen values and the published molecular masses of fibrinogen and average D-dimer. The characteristics of five latex enhanced D-dimer immunoassays were also tested against early and late fibrin fragments using this procedure. These were produced by prolonged fibrinolysis of a set of patient samples of varying fibrinogen concentrations.


RESULTS
These varied typically between methods and lysis times. One of the methods showing the highest yield irrespective of lysis time was used for calibration. A linear standard curve with zero intercept and R2 = 0.95 was obtained.


CONCLUSIONS
Following this procedure will allow better transferability of D-dimer in future clinical trails.
Edlund
Bror
B
Department of Clinical Chemistry, Orebro University Hospital, SE-70185 Orebro, Sweden. bror.edlund@orebroll.se
Nilsson
Torbjörn K
TK
D001681:Biological Assay / Q000379:methods; D002138:Calibration; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis* / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism; D005343:Fibrinolytic Agents / Q000494:pharmacology; D006801:Humans; D012044:Regression Analysis; D015203:Reproducibility of Results; D010959:Tissue Plasminogen Activator / Q000494:pharmacology
D005338:Fibrin Fibrinogen Degradation Products; D005343:Fibrinolytic Agents; C036309:fibrin fragment D; D005340:Fibrinogen; D010959:Tissue Plasminogen Activator