Establishment of reference intervals for aldosterone and renin in a Caucasian population using the newly developed Immunodiagnostic Systems specialty immunoassay automated system.

BACKGROUND: Measurement of aldosterone and/or renin is essential to aid the differential diagnosis of secondary hypertension, guide strategy for therapeutic management of hypertension and assess adequacy of mineralocorticoid replacement. AIM: The objective was to establish normative data for aldosterone and renin using the Immunodiagnostic Systems specialty immunoassay system platform in a Caucasian population. METHODS: Following informed consent, 365 subjects were recruited to this study. Subjects were ambulatory and attended clinic for blood pressure measurement and phlebotomy between the hours of 7:00 and 11:00. Blood pressure was measured according to the 2013 European Society of Hypertension/Cardiology guidelines. The inclusion criteria: age ≥18 years, BMI <30 kg/m(2), non-pregnant, blood pressure <140/90, normal electrolytes and kidney function and not taking prescribed/over the counter medications. Ninety-four subjects were excluded based on these criteria. A total of 271 volunteers (females n = 145), aged 18-65 years formed the reference cohort. Blood for aldosterone/renin was collected into ethylenediaminetetraacetic acid specimen tubes. Samples were kept at room temperature and transported within 30 min of blood draw to the laboratory for immediate processing (centrifugation, separation and freezing of plasma). Plasma was stored at -20℃ prior to analysis on the Immunodiagnostic Systems specialty immunoassay system instrument. RESULTS: The established reference intervals in an Irish Caucasian population for renin: females: 6.1-62.7 mIU/L, males: 9.0-103 mIU/L, for aldosterone: females: <138-1179 pmol/L, males: <138-670 pmol/L, respectively. CONCLUSION: This study demonstrates that reference intervals for aldosterone and renin should be gender specific. These automated immunoassays offer rapid stratification of patients with refractory hypertension and will better facilitate the optimization of therapeutic management.

Reference intervals for aldosterone, renin, and the aldosterone-to-renin ratio in the population-based Study of Health in Pomerania (SHIP-1).

The renin-angiotensin-aldosterone system plays a key role in the regulation of human blood pressure. The aldosterone-to-renin ratio (ARR) is widely accepted for screening the primary hyperaldosteronism (PAL). Various cutoffs for positive PAL screening have been defined in patient cohorts from endocrinological referral centers and primary care. However, the distribution of the ARR in the general population is largely unknown. We aim to provide reference ranges for plasma aldosterone concentration (PAC), plasma renin concentration (PRC), and the ARR for the general population of north-east Germany. A cohort of 3 300 subjects participated in the first follow-up of the longitudinal, population-based Study of Health in Pomerania (SHIP). PAC and PRC were measured by radioimmunometric procedures. The reference interval was defined as the central 95% range between the 2.5(th) and 97.5(th) percentiles. A reference population comprising 1,347 healthy subjects was selected. Sex and age-specific (25-54 and 55-74 years) reference ranges are presented. The upper reference limit for the ARR was 14.2 and 20.3 in younger, and 22.4 and 25.5 in older men and women, respectively. Time of blood sampling had no influence on the ARR, while beta blockers, and agents acting on the renin-angiotensin system were associated with higher and lower ARR, respectively. Our upper reference limit for the ARR is clearly lower than previously reported values from studies of hypertensive patients in primary care or hypertension referral centers. We confirm that PAC and PRC are associated with various factors, including sex, age, intake of estrogen, and various antihypertensive medications.

Functional tests for primary aldosteronism: value of captopril suppression.

With the introduction of more simple screening tests such as the aldosterone/renin ratio, the detection rate of primary aldosteronism has increased considerably. Until now, no reference values have been available for reporting the aldosterone/renin ratio using plasma aldosterone values expressed in SI units (pmol/L) and plasma active renin (ng/L) measured by immunoradiometric assay. We studied 153 subjects who had either normal blood pressure, essential hypertension, or primary aldosteronism. Essential hypertensive patients usually have aldosterone/renin (pmol/L/ng/L) ratios below 100, whereas ratios for patients with primary aldosteronism are above 140. Results that fall between 100 and 140 suggest a need for repeat testing. Patients with elevated aldosterone/renin ratios require confirmatory testing to demonstrate nonsuppressive autonomous aldosterone production. To this end, salt loading is widely used, but this approach may be contraindicated in patients with severe hypertension. The captopril suppression test appears as effective as salt loading in confirming a diagnosis of primary aldosteronism. In addition, the captopril test is safe, well tolerated, and cost-effective.