Immunonephelometric measurement of human plasma apolipoproteins A-I and A-II: an assay performed by consecutive addition of the two antisera to a single specimen.

A consecutive immunonephelometric assay for human apolipoproteins (apo) A-I and A-II is described and validated. Apo A-II is first measured from guanidine-HCl-treated samples using a monospecific antiserum raised in sheep against purified apo A-II. This is followed by addition of anti apo A-I serum to the same tubes and recording of the light scattering after 90 min. The results of 125 serum samples were compared with those obtained by the radial immunodiffusion method, and thereby, correlation coefficients of 0.98 and 0.91 could be calculated for apo A-I and apo A-II concentrations, respectively. The within-assay variations of apo A-I and apo A-II methods were 3.28% and 2.40%, respectively, the corresponding inter-assay variations were 7.76% and 8.90%.