ASSAY OF D-DIMER BASED ON IMMUNOFILTRATION AND STAINING WITH GOLD COLLOIDS

In this immunofiltration assay of D-dimer in plasma samples, the antig ens are captured by a monoclonal antibody on a porous membrane, and la beled with the same antibody conjugated to gold colloids. The assay ti me is <2 min, and a color of intensity proportional to the concentrati on of D-dimer is left on the membrane. The reference range (mean +/- 2 SD) was 0.336 +/- 0.133 mg/L (n = 69). Linearity was found up to 10 m g/L. Comparison with ELISA results (x) for 198 patients' samples demon strated a linear regression equation of y = 0.99(+/- 0.05)x + 0.68(+/- 0.07) and a mean square error of 0.503. Comparison of visual reading of the color signal (y) vs reflectometric measurements (x) for 220 pat ients' samples demonstrated a linear regression equation of y = 2.5(+/ - 0.06)x - 0.22(+/- 0.04) and a mean square error of 0.095. Bilirubin, hemoglobin, fibrinogen, soluble fibrin, and fibrinogen degradation pr oducts and freezing/thawing of samples did not interfere. Some interfe rence from rheumatoid factor, heparin, and the presence of cells or la rge lipid particles was seen. The variance (CV) was 8-12% within run, 10-18% between runs, and 13-20% between persons. The new assay constit utes a rapid and reliable analytical tool combining simplicity equival ent to that of latex tests with analytical information approaching tha t of ELISA.