Analytical validation and investigation on reference intervals of aldosterone and renin in Chinese Han population by using fully automated chemiluminescence immunoassays.

BACKGROUND: The aldosterone/renin ratio (ARR) is recommended to screen for primary aldosteronism (PA) in hypertension. We estimated fully automated chemiluminescence immunoassays (CLIA) for plasma aldosterone concentrations (PAC) and plasma direct renin concentrations (PRC) and investigated their reference intervals in Chinese Han population.

METHODS: PAC and PRC were measured on a fully automated analyzer (LIAISON XL, DiaSorin, Italy). Performance characteristics were estimated according to CLSI approved guidelines. 328 healthy individuals were selected for reference intervals investigation. Results simultaneously tested by CLIA and radioimmunoassays were reviewed from 123 patients with hypertension and/or adrenal space-occupying lesion. PAC/PRC ratio (ARRprc ) was compared to PAC/plasma renin activity (PRA) ratio (ARRpra ).

RESULTS: Within-laboratory imprecision was 5.6%-6.7% for PAC and 3.0%-3.3% for PRC. The LoQ was 72.2 pmol/L for PAC and 1.27 mIU/L for PRC. Linearity was excellent in the range of concentrations between 94 and 2708 pmol/L for PAC and 1.3-461.8 mIU/L for PRC. Interferences of hemoglobin, unconjugated bilirubin and lipaemia could be acceptable, but not of conjugated-bilirubin when renin and aldosterone at low concentrations. The central 95% reference intervals for males: PAC: 76-722 pmol/L, PRC: 3.3-92.7 mIU/L, ARR: 2.2-46.0 pmol/mIU; for females: PAC: 85-1010 pmol/L, PRC: 3.7-99.8 mIU/L, ARR: 3.6-68.4 pmol/mIU. Upper reference limits for ARR of younger and older men were lower than women. ARRprc and ARRpra showed almost perfect agreement (kappa = 0.815) for screening PA.

CONCLUSION: The DiaSorin tests are valuable analytical options for PAC and PRC measurements. We recommend sex-specific and age-specific reference intervals of these items should be estimated.