BACKGROUND Lipoprotein(a) [Lp(a)] is an important cardiovascular risk factor, but clinical immunoassays are flawed. Apolipoprotein(a) [apo(a)], the characteristic protein of Lp(a), contains a variable number of kringle repeats (size isoforms) that make accurate measurement of Lp(a) difficult. We developed a sandwich enzyme immunoassay that uses a murine monoclonal anti-apo(a) antibody for capture and a polyclonal anti-apolipoprotein B (apo B) for detection. Because Lp(a) contains one molecule each of apo(a) and apo B, the assay measures the number of Lp(a) particles [Lp(a)-P] in the circulation without bias due to apo(a) size isoforms. METHODS After developing and choosing the best anti-apo(a) clone for Lp(a) capture, we identified suitable reagents and ELISA conditions, and validated assay performance (precision, linearity, limit of detection, interferences, and apo(a) size isoform bias). RESULTS The Lp(a)-P assay was precise with within-run precision of 5.5% to 7.2% and total imprecision of 6.9% to 12.1%. The assay had a limit of detection of 13 nmol/l and was linear from 2 to 499 nmol/l. There was no interference from plasminogen or apolipoprotein B up to 80 and 200 mg/dl, respectively, and bias plot showed no bias related to apo(a) size (kringle 4 type 2 repeats). CONCLUSIONS Lp(a)-P assay is sensitive, precise and linear over a wide analytical range and is a suitable alternative for laboratories concerned about inaccuracy due to apo(a) size polymorphism and the poor performance of immunoturbidimetric assays.

中文翻译：

---

脂蛋白（a）颗粒数目测定，无载脂蛋白（a）大小同工型错误。

背景技术脂蛋白（a）[Lp（a）]是重要的心血管危险因素，但是临床免疫测定存在缺陷。载脂蛋白（a）[apo（a）]是Lp（a）的特征蛋白，包含可变数量的kringle重复序列（大小同工型），这使得难以准确测量Lp（a）。我们开发了一种夹心酶免疫测定法，该方法使用鼠类单克隆抗apo（a）抗体进行捕获，并使用多克隆抗载脂蛋白B（apo B）进行检测。由于Lp（a）分别包含apo（a）和apo B的一个分子，因此该测定法可测量循环中Lp（a）颗粒[Lp（a）-P]的数量，而不会因apo（a）大小同工型而产生偏差。方法开发并选择最佳的抗apo（a）克隆进行Lp（a）捕获后，我们确定了合适的试剂和ELISA条件，并验证了测定性能（精度，线性，检测限，干扰和apo（a）大小异构体偏差）。结果Lp（a）-P测定非常精确，内部分析精密度为5.5％至7.2％，总不精密度为6.9％至12.1％。该测定的检出限为13 nmol / l，线性范围为2至499 nmol / l。分别高达80和200 mg / dl的纤溶酶原或载脂蛋白B均无干扰，偏倚图显示与apo（a）大小无相关的偏倚（kringle 4 2型重复）。结论Lp（a）-P检测在宽泛的分析范围内灵敏，精确和线性，对于担心由于apo（a）大小多态性和免疫比浊法性能不佳而引起的不准确性的实验室，它是一种合适的选择。该测定的检出限为13 nmol / l，线性范围为2至499 nmol / l。分别高达80和200 mg / dl的纤溶酶原或载脂蛋白B均无干扰，偏倚图显示与apo（a）大小无相关的偏倚（kringle 4 2型重复）。结论Lp（a）-P检测在宽泛的分析范围内灵敏，精确和线性，对于担心由于apo（a）大小多态性和免疫比浊法性能不佳而引起的不准确性的实验室，它是一种合适的选择。该测定的检出限为13 nmol / l，线性范围为2至499 nmol / l。分别高达80和200 mg / dl的纤溶酶原或载脂蛋白B均无干扰，偏倚图显示与apo（a）大小无相关的偏倚（kringle 4 2型重复）。结论Lp（a）-P检测在宽泛的分析范围内灵敏，精确和线性，对于担心由于apo（a）大小多态性和免疫比浊法性能不佳而引起的不准确性的实验室，它是一种合适的选择。