INTERFERENCE OF LYSOPHOSPHATIDYLCHOLINE IN HORMONE RADIOIMMUNOASSAYS

The interference of synthetic and naturally occurring detergents in im munoassays is well documented. In the present study, we evaluated the effect of lysophosphatidylcholine (LPC) and found that the lysophospho lipid interfered with formation of the antigen-antibody complex in hor mone immunoassays. In the presence of LPC (100 mumol/L), progesterone was overestimated by 29%. Furthermore, physiological concentrations of LPC (140 mumol/L) interfered with the assays of cortisol, progesteron e, and aldosterone, resulting in overestimations of 35%, 30%, and 27%, respectively. The addition of albumin decreased the interference by L PC to 7% in the assay of cortisol and progesterone when the LPC:albumi n ratio was unity. Adding cholesterol (100 mumol/L) also reduced by 50 % the interference induced by LPC. Finally, treating plasma to increas e the endogenous LPC concentration also resulted in interference in th e cortisol assay. Thus, interpretation of the results of these assays should take into consideration the endogenous serum albumin:LPC ratio.