Endocrine Abstracts

The purpose of our study was to establish an assay for the measurement of aldosterone in saliva which utilises a simple, non-invasive sampling technique on an out-patient basis. For this we have developed a non-isotopic, time-resolved fluorescence immunoassay. The assay only requires a volume of 100 μl for each duplicate value obtained and involves an overnight incubation after extraction of samples. Cross-reactivity with potentially interfering steroids is below 0.01%. The assay has a dynamic range of 30 to 2000 pg/ml. The protocols used for clinical validation of the assay in healthy volunteers as well as patients were all approved by the local ethics committee of the medical faculty. The intra-assay coefficients of variation were between 8.5 and 15.4% for values between 209.2 and 46.2 pg/ml respectively. We found a significant correlation between plasma and saliva values (n=125), (r²=0.797, P<0.0001). Saliva values were around 22% of those observed in plasma. In 5 out of 10 healthy volunteers who were tested for a day profile by simultaneous saliva and plasma aldosterone sampling, there was corresponding variability throughout the day although a distinct circadian rhythm was not apparent. The remaining 5 subjects had values close to or below the limit of quantification. In 5 patients undergoing ACTH stimulation test, a significant increase in salivary aldosterone concentration from 68.3±30.1 pg/ml to 212.3±68.8 pg/ml was observed after 60 minutes of administration. In two patients with confirmed Conn’s syndrome, mean salivary aldosterone values were higher (153.1±55.8 pg/ml) throughout the day compared to those of healthy volunteers (49.9±31.3 pg/ml). The preliminary findings in two subjects with confirmed Conn’s support the idea of detecting hypersecretion of aldosterone by multiple sampling rather than a single random aldosterone determination. In conclusion, this assay provides a non-invasive, easy screening method to analyse aldosterone secretion.