Confounding results of Lp(a) lipoprotein measurements with some test kits.

A small number of recent studies have reportedly failed to detect the well-established association between a high Lp(a) lipoprotein level and coronary heart disease (CHD). This has made some workers question the importance of a high Lp(a) lipoprotein level as a CHD risk factor. However, serious problems with some of the commercially available test kits, inadequate test techniques or failure to consider the lability of the Lp(a) lipoprotein particle are more plausible explanations of the confounding results. The problems with some of the commercially available test kits include lack of standardization and validation; risk of cross-reactivity with plasminogen or other serum proteins; failure to consider potential problems when measuring samples with varying length of the Lp(a) polypeptide chain (i.e. failure to cope with the isoform variation); non-divulgence of contents of test reagents; and pretreatments of samples that drastically change the Lp(a) lipoprotein particles from their native state. Any test system should be validated at the scientific level before it is assumed to provide correct measurements of Lp(a) lipoprotein level in serum. New test kits should be safely anchored in validation in one of the research laboratories active in the area, before they are put on the market. As new batches are produced, the quality of every new batch of test kits should be monitored on a long-term basis in collaboration with a research laboratory.