Aldosterone determination: comparison of a RIA assay and a CLIA assay.

OBJECTIVE: To extend knowledge about the clinical performances of a new chemiluminescent immunoassay (CLIA) for aldosterone set up in available analysers. DESIGN AND PATIENTS: We compared the results of a RIA assay to those of a CLIA assay in 198 serum and 80 urine samples from patients in endocrine and hypertension departments. Furthermore, for serum samples the concordance of results for postural tests was analysed. RESULTS: RIA and CLIA aldosterone serum concentration was linearly correlated with a slope of 0.988 and an intercept of 70.4pmol/L. The variations of aldosterone serum concentration obtained with the two assays during postural tests were very consistent. There was no significant difference of aldosterone concentrations after thawing with the CLIA assay. RIA and CLIA aldosterone urine concentrations were linearly correlated with a slope of 0.787 and an intercept of -2.64nmol/L. Omitting the preservative boric acid from urine samples did not modify aldosterone concentration at least up to 48h after collection. CONCLUSION: The RIA and CLIA assays were well correlated for the most useful serum samples. It is well suited to circumvent isotopic assays with the throughput of available analysers.