Analytical performance of a sandwich enzyme immunoassay for preβ1-HDL in stabilized plasma

We have established an immunoassay for prebeta1-HDL (the initial acceptor of cellular cholesterol) using a monoclonal antibody, MAb55201. Because prebeta1-HDL is unstable during storage, fresh plasma must be used for prebeta1-HDL measurements. In this study, we describe a method of stabilizing prebeta1-HDL, and evaluate the analytical performance of the immunoassay for prebeta1-HDL. Fresh plasma was stored under various conditions with or without a pretreatment consisting of a 21-fold dilution into 50% (v/v) sucrose. Prebeta1-HDL concentration was measured by immunoassay: In nonpretreated samples, prebeta1-HDL decreased significantly from the baseline after 6 h at room temperature. Although prebeta1-HDL was more stable at 0degreesC than at room temperature, it increased from 30.2 +/- 8.5 (SE) to 56.5 +/- 5.5 mg/1 apolipoprotein A-I (apoA-1) (P < 0.001) in hyperlipidemics, and from 18.4 +/- 1.2 to 37.9 +/- 3.3 mg/l apoA I (P < 0.001) in normolipidemics after 5-day storage. After 30-day storage at -80 degreesC, prebeta1-HDL increased from 29.0 +/- 4.0 to 38.0 +/- 5.7 mg/1 apoA-I (P < 0.001) in hyperlipidemics, whereas it did not change in normolipidemics. In pretreated samples, prebeta1-HDL concentration did not change significantly under any of the above conditions. Moreover, prebeta1-HDL concentrations determined by immunoassay correlated with those determined by native two-dimensional gel electrophoresis (n = 24, r = 0.833, P < 0.05). An immunoassay using MAb55201 with pretreated plasma is useful for clinical measurement of prep 1-HDL.