An indirect sandwich ELISA for LP(a) in serum and dried blood spots.

We have established a reproducible and inexpensive indirect sandwich ELISA for Lp(a) quantitation in both serum and dried blood spot samples. All reagents used in the assay are available commercially. The intra-assay CVs were 3.8 +/- 0.9% for serum and 4.5 +/- 1.7% for dried blood spots on filter paper. The inter-assay CVs were 6.3 +/- 2.3% and 4.5 +/- 0.1% for serum and dried blood spot, respectively. Lp(a) concentrations measured by the ELISA and a commercial RIA were highly correlated (r = 0.989, n = 60, P less than 0.001). However concentrations measured by RIA were 34.3% +/- 9.7% higher than those by ELISA. Lp(a) concentrations in serum and in dried blood spots were also highly correlated (r = 0.966, n = 40, P less than 0.001). This indirect ELISA is suitable for assaying large numbers of serum or dried blood spot samples. However, the differences between the concentrations measured by ELISA and RIA stress the need for standardization of Lp(a) measurements.