Poor correlation between soluble fibrin concentrations measured by two commercially available immunoassays

Soluble fibrin (SF) has attracted considerable interest as a marker for haemostatic activation. Two new enzyme immunoassays for SF, Enzymun-Test FM (Boehringer Mannheim, Germany) and Fibrinostika Soluble Fibrin (Organon Teknika, Belgium) have recently become commercially available. We measured plasma levels of SF in clinically obtained blood samples in order to compare the two new assays. Blood was drawn from 10 healthy volunteers and from 149 patients on the first day after surgery for fractures of the upper part of the femur. Collection and processing was done according to the manufacturers' recommendations. In the patients, levels found by the two assays were significantly different. The Enzymun-Test assay reported a median (range) of 11.87 (2.66 - > 62.20) mg/l, whereas the Fibrinostika assay found a median (range) of 3.34 (1.08 - >10) mg/l. The correlation coefficient was 0.38 (Spearman). A poor correlation was thus found between values obtained by the two assays in the patient category chosen. Further validation of the assays is necessary.