The detection of D-dimer in plasma by enzyme immunoassay: improved discrimination is obtained with a more specific signal antibody.
Most commercial D-dimer enzyme immunoassays employ two antibodies, a fibrin specific capture monoclonal and a less specific antibody cross-reacting with epitopes present on fibrinogen. Two different ELISA systems were compared to test whether this cross-reaction can lead to overestimation of the true levels of cross-linked fibrin derivatives. Both assays used the same D-dimer specific antibody for capture, DD-3B6/22, but utilized signalling antibodies which differed in fibrinogen reactivity. The assays gave low results for 210 normal samples (conventional ELISA, 39 +/- 45 ng/ml; non-fibrinogen reactive ELISA, 23 +/- 20 ng/ml) with a high degree of elevation for 53 patients with active thrombosis (conventional ELISA, 901 +/- 649 ng/ml; non-fibrinogen reactive ELISA, 1,906 +/- 1,725 ng/ml). However, a dramatic difference between results was seen when fibrinogenolysis was induced by treatment of 20 normal plasmas with high levels of t-PA and plasminogen. The D-dimer levels estimated with the conventional fibrinogen-reactive signal antibody rose 25-fold (normal, 36 +/- 27 ng/ml; treated, 833 +/- 272 ng/ml), whereas no increase was obtained with the non-fibrinogen reactive ELISA (normal, 24 +/- 21 ng/ml; treated, 27 +/- 22 ng/ml). These results suggest that a more accurate estimation of D-dimer levels in samples containing high levels of fibrinogen derivatives is achieved in assays incorporating non-fibrinogen reactive antibodies.
Hart
R
R
AGEN Biomedical Ltd, Queensland, Australia.
Bate
I
I
Dinh
D
D
Elms
M
M
Bundesen
P
P
Hillyard
C
C
Rylatt
D B
DB
D000293:Adolescent; D000328:Adult; D000918:Antibody Specificity; D000933:Antifibrinolytic Agents / Q000032:analysis*; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D000939:Epitopes; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D008297:Male; D010958:Plasminogen; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013927:Thrombosis / Q000097:blood; D010959:Tissue Plasminogen Activator
D000933:Antifibrinolytic Agents; D000939:Epitopes; D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D; D010958:Plasminogen; D010959:Tissue Plasminogen Activator