Abstract: The invention relates to a process for the quantitative determination of a serum protein, especially apolipoprotein, in turbid serum or plasma samples by nephelometry, which comprises, after having carried out an immunologic reaction with the corresponding antibody, measuring in the presence of a tenside of the formulaCH.sub.3 --(CH.sub.2).sub.m --R--(CH.sub.2 --CH.sub.2 --O).sub.n --H (I)in which ##STR1## Y is H-- or CH.sub.3 --(CH.sub.2).sub.q --, m and q, being identical or different; each are an integer of from 6 to 26, preferably 6 to 18; n is an integer of from 7 to 50, preferably 7 to 25; and x is 7 or 8; the tenside being used in a concentration of from 10.sup.-3 to 10.sup.-1 % by volume.

Abstract: Lipids in blood serum are directly determined by extracting the pre-.beta.-lipoprotein (very low density lipoprotein) and chylomicrons and .alpha.-lipoproteins (high density lipoproteins) from the serum by treatment of the serum with a polycation and optionally wih a weak ion exchanger and/or a strongly polar lipophilic adsorber, and then measuring the lipid content of the .beta.-lipoproteins in the serum.