The Clinical Value of Salivary Aldosterone in Diagnosis and Follow-Up of Primary Aldosteronism.

Primary aldosteronism (PA), the most common form of secondary hypertension, causes relevant morbidity. The value of salivary measurements of aldosterone in clinical routine in PA so far has not been assessed. First, we analyzed salivary and plasma aldosterone concentrations of 42 patients with PA and 37 hypertensive controls (HC) during a sodium infusion test prospectively. Second, morning salivary and plasma aldosterone concentrations as well as diurnal saliva aldosterone profiles were analyzed in 115 patients treated for PA (46 adrenalectomy, 56 spironolactone, 13 eplerenone). Salivary aldosterone was substantially elevated in PA patients compared to HC at baseline (106±119 vs. 40±21 ng/l, p=0.01), and after 4-h sodium infusion test (60±36 vs. 23±14, p=0.01). Positive correlation between salivary and plasma aldosterone levels was evident, with exception of concentrations in or below the lower normal range. Applying a salivary aldosterone cutoff of 51.2 ng/l, found by ROC curve analysis, rendered a sensitivity of 81% and a specificity of 73% for PA. The diurnal rhythm of aldosterone was preserved in untreated PA patients, but concentrations were higher in the context of PA, and normalized after surgery (118±57 vs. 31±18 ng/l, p<0.01). Taken together, salivary aldosterone measurements correlate with plasma levels, allowing simple and cost effective assessments of aldosterone secretion in an outpatient setting. Nevertheless, as this method alone cannot replace other plasma parameters, and as aldosterone profiling would not alter diagnostic or treatment strategies, salivary aldosterone measurements in routine practice are of limited clinical value.

Screening for primary aldosteronism in hypertensive subjects: results from two German epidemiological studies.

OBJECTIVE: The prevalence of primary aldosteronism in unselected hypertensive patients is currently unknown. We investigated the frequency of positive screening results for primary aldosteronism based on the aldosterone-to-renin ratio (ARR) in hypertensive subjects aged 30-79 years from two German epidemiological studies. We further examined the frequency of positive screening results in subjects with resistant hypertension or stage III hypertension and assessed possible disparities between untreated and treated hypertensive subjects. METHODS: Data were obtained from the first follow-ups of the population-based study of health in Pomerania (SHIP; n=1392) and the cooperative health research in the region of Augsburg (KORA; n=1052). Study-specific reference ranges for plasma aldosterone concentration (PAC), plasma renin concentration (PRC) and the ARR were applied. Confirmation tests for primary aldosteronism were not performed in these epidemiological studies.Three definitions for a positive screening for primary aldosteronism were applied: A) increased ARR; B) increased ARR and decreased PRC; and C) increased ARR and increased PAC and decreased PRC. RESULTS: The frequency of positive screening results was 7.0, 3.8 and 0.2% according to definitions A-C respectively. In the subgroups of subjects with resistant hypertension (11.9, 5.5 and 0.9%) or stage III hypertension (18.3, 14.0 and 1.1%), these frequencies were markedly higher than those in the general hypertensive population. There was no difference in the frequency of positive screening results between the treated and untreated hypertensive subjects. CONCLUSIONS: A maximum of 7.0% of the hypertensive population in Germany shows a positive screening result for primary aldosteronism. Thus, primary aldosteronism may be less frequent than previously expected based on data from referred hypertensive patients.

Salivary aldosterone as a diagnostic aid in primary aldosteronism.

Recent evidence demonstrates an increased incidence of primary aldosteronism (PA) in approximately 10% of the hypertensive population, making noninvasive and simple screening methods necessary. The aim of the present study was to apply a time-resolved fluorescence immunoassay for the measurement of aldosterone in saliva and the establishment of a cut-off to identify patients with a high likelihood for PA requiring subsequent screening with the aldosterone to renin ratio. Saliva was collected (AM and PM) to ascertain an optimum time with best discriminating power between healthy and disease states. Plasma aldosterone, after overnight recumbency and 4 h later, was collected for posture testing. The participants included 53 PA patients (aged 14-78), 54 with essential hypertension (EH, aged 19-82), and 38 healthy volunteers (aged 19-56). Saliva aldosterone (SA) (median, 25-75(th)%) in PA was found at 90 pg/ml (61-139) compared to 53 pg/ml (40-85) in EH, with discrimination between PA versus EHs best in the morning (cutoff: 81 pg/ml, 77% sensitivity, 82% specificity). Saliva aldosterone decreases throughout the day in patients with adenomas [APA AM: 123 pg/ml (92-213) vs. PM: 79 pg/ml (41-116)], but not in those with bilateral hyperplasia [BAH AM: 85 pg/ml (59-115)] vs. pm 69 pg/ml (57-114). Morning SA alone allows discrimination between PA and controls, though with significant overlap against EHs, leading to a high number of false positives. More promising is the use of diurnal variation in SA in distinguishing between APA and BAH. The decline in SA seen in patients with APA presents a more constant finding compared to posture testing, which fails to correctly classify a large number of patients.

Saliva as a medium for aldosterone measurement in repeated sampling studies.

BACKGROUND: Saliva is a readily available biological fluid, making it convenient in diagnosis of diseases and in multi-sampling protocols. Several salivary steroids give a useful index of free plasma levels. Increased incidence of primary aldosteronism (PA) in approximately 10% of the hypertensive population has increased interest in the mineralocorticoid aldosterone. METHODS: A biotinylated-aldosterone tracer and a commercially available antibody are used in a time-resolved fluorescence immunoassay (TR-FIA) to measure salivary aldosterone (SA). Saliva was collected in various multi-sampling protocols: Investigation of diurnal rhythm in healthy and PA patients, ACTH stimulation test and posture test in healthy subjects. RESULTS: Method validation showed a sensitivity of 19 ng/L and intra-/inter-assay precision between 7.2-10.1% and 8.7-15.7%, respectively. SA correlated significantly (y = 0.2995x +/- 0.01, r(2)=0.60) to plasma aldosterone measured by a commercial radioimmunoassay. SA (median; 95%CI) was at 111 (95-127)ng/L in PA (n=84) and 50 (44-56)ng/L in healthy subjects (n=60). After change in posture, aldosterone increased in both, saliva (57 (47-63)ng/L to 95 (84-117)ng/L) and plasma (26 (26-41)ng/L to 135 (110-181)ng/L). Peak levels were reached after 1h, and were higher in females than in males. CONCLUSIONS: SA correlates well to plasma aldosterone and mirrors responses during conditions of stress. SA is significantly higher in PA, and the diurnal rhythm seen in the healthy is blunted in PA. We additionally found gender-dependent differential responses to posture, with higher increases in females. Measurement of aldosterone in saliva presents a useful and convenient method for application in multi-sampling studies.

A highly sensitive immunofluorometric assay for the measurement of aldosterone in small sample volumes: validation in mouse serum.

Data on the involvement of aldosterone in the regulation of the renin-angiotensin-aldosterone system (RAAS) in rodents are still scarce, partly due to the high sample volumes needed by commercially available assays and to the very low aldosterone concentrations present. We have developed a highly sensitive and non-isotopic immunoassay, requiring a volume of only 50 microl serum for a duplicate measurement, employing a highly specific monoclonal antibody against aldosterone. The assay was validated in human and mouse samples and exhibited a linear working range from 10 to 1000 pg/ml. Values obtained after a chromatographic purification step correlated significantly to the dichloromethane extraction ordinarily used. Basal aldosterone values were measured in 75 mouse hybrids and found within the linear range (173+/-21 pg/ml), with no significant difference between males and females. Additionally, we show an increase in serum aldosterone in mice from 3 to 11 weeks of age. Mice of the same genetic background were treated with dexamethasone intraperitoneally (n=7), resulting in significantly decreased concentrations (35+/-3 vs 114+/-33 pg/ml in controls; P<0.001). In contrast, adrenocorticotropic hormone resulted in significantly increased serum aldosterone (603+/-119 pg/ml; n=7; P<0.001), as did the physiological stimulation of the RAAS by a high K(+)/low Na(+) diet (1369+/-703 vs 172+/-36 pg/ml). In conclusion, we have developed and validated an extremely sensitive assay for determination of aldosterone concentrations from very small serum samples, which could be especially useful in pharmacological intervention studies in rodent models.