Supraregional Interlaboratory Quality-Control Survey for an Immunoradiometric Renin Assay

For the last 20 years, the most widely used method for assessment of the renin-angiotensin system has been the plasma renin activity assay (1). Although the assay gives useful information on the enzymatic function of the renin molecule, the intrinsic characteristics of this method limit its analytical accuracy (2). Immunoradiometric assays for renin, developed in 1985, overcame this limitation of the enzymatic assay because the well-defined monoclonal antibodies provided the means for direct quantification of specific active forms of the enzyme molecule (3)(4). Nevertheless, a critical debate has developed over the use of these assays (5)(6)(7)(8)(9)(10). A pilot study (11)(12) in a limited number of laboratories (eight Italian centers) found satisfactory indexes of precision for a direct immunoradiometric renin assay (Eria Diagnostics, Sanofi-Pasteur). In our previous experience, the inter- and intralaboratory reproducibility indices of this commercial immunoradiometric assay appeared to be better than those that had been achieved with an enzymatic assay (REN-CTK; Sorin Biomedica), with the differences probably being attributable to the greater complexity of the procedure for the latter assay (11). Various reports have been published during the past 30 years describing useful tools to monitor the performance of immunoassays …