Overestimation of Aldosterone by Immunoassay in Renal Impairment

[摘要] To the Editor:Accurate measurements of aldosterone are important in the differentiation of various disorders of the renin–angiotensin–aldosterone axis. Aldosterone is commonly measured in clinical laboratories by direct immunoassay without solvent extraction. We report that plasma aldosterone is overestimated by a widely used automated chemiluminescent immunoassay (Diasorin Liaison) in patients with renal impairment. This effect is not confined to end-stage renal failure, but occurs also in graded fashion in patients with mild or moderate renal impairment.We performed aldosterone measurements by the Liaison (DiaSorin) chemiluminescent immunoassay method before and after solvent extraction on 86 outpatient plasma samples. These comprised samples from 41 patients with varying degrees of renal impairment, 21 controls [estimated glomerular filtration rate (eGFR) >90 mL · min−1 · (1.73 m2)−1] and 24 patients on hemodialysis. Solvent extraction was performed by adding 3 mL of dichloromethane to 0.6 mL of serum, and the mixture was agitated on a gentle rocker for 10 min. After standing for 30 min, 1.5 mL of the hydrophobic fraction was evaporated to dryness and reconstituted in 0.3 mL Cobas universal diluent (Roche). The typical interbatch analytical CV was 9.4% at 10.5 ng/dL (292 pmol/L) and 6.0% at 32.4 ng/dL (899 pmol/L). In 15 …

[学科分类] 过敏症与临床免疫学