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Lipoprotein(a) concentration and risk of atherothrombotic disease.

To the Editor. —In their article, Dr Ridker and colleagues 1 reported that there was no prospective association between lipoprotein(a) [Lp(a)] concentration and the risk of stroke. The authors summarized briefly the results of prior prospective studies of Lp(a) as a risk factor for coronary artery disease; however, certain points raised in that discussion require clarification. Namely, two studies that used the arbitrary nomenclature "apo (a)" for apolipoprotein (a) as opposed to "Lp(a)" were addressed separately. With one exception, 2 all studies to date have detected Lp(a) using immunoassays directed against apo(a). For example, Ridker et al 1 refer to "Lp(a)" and Wald et al 3 in the article cited by Ridker et al refer to "apo(a)"; however, both groups used the Biopool ELISA (enzyme-linked immunosorbent assay). Thus, it is neither necessary nor appropriate to dichotomize studies based on differences in nomenclature. Therefore, among prior prospective studies of Lp(a) and