MEASUREMENT OF LIPOPROTEIN(A) - COMPARISON OF MACRA(TM) AND IMUBIND(R) METHODS

Our specific aim was to compare lipoprotein(a) [Lp(a)] measured by two enzyme-linked immunosorbent assays (the Strategic Diagnostics, Inc. M acra(TM) Lp(a) and the American Diagnostica, Inc. Imubind(R) Lp(a) Str ipwell) in sequentially referred hyperlipidemic patients. The Macra(TM ) method binds Lp(a) in serum or plasma to monoclonal anti-Lp(a) in mi crotiter test wells followed by polyclonal anti-Lp(a) and a chromogeni c reaction; the Imubind(R) method is similar but uses two polyclonal a nti-Lp(a) antibodies. Within run coefficients of variation were 1.5 pe rcent for the Macra(TM) (Lp[a] 27.2 +/- 0.4 mg/dl) and 3.4 percent for the Imubind(R) method (Lp[a]=18.9 +/- 0.6 mg/dl). Between-run coeffic ients of variation for the Macra(TM) method were 4.7 percent (Lp[a] 14 .8 +/- 0.7 mg/dl) and 8.3 percent (Lp[a] of 33.5 +/- 2.8 mg/dl). For t he Imubind(R) method in nine separate analytical runs, the between run coefficients of variation were 8.4 per-cent (Lp[a] of 15.4 +/- 1.3 mg /dl), 3.0 percent (18.8 +/- 0.6 mg/dl), and 5.7 percent (25.6 +/- 1.5 mg/dl). The intraclass correlation was 0.92 (p less than or equal to 0 .0001) for duplicate aliquots (n=210) quantitated by both methods, and the lower limit of the 95 percent confidence interval of the intracla ss correlation was 0.90. Comparison of the two methods revealed no sys tematic bias (p=0.09); since the lower limit of the 95 percent intracl ass correlation confidence interval was greater than or equal to 0.75, the two methods for measuring Lp(a) are considered interchangeable. G iven the importance of Lp(a) as an independent risk fact-or for corona ry heart disease, it is clinically important to have precise and accur ate methods for its measurement.