Saliva as a medium for aldosterone measurement in repeated sampling studies

Area of Science:

• Endocrinology
• Clinical Chemistry
• Biomarker Discovery

Background:

• Saliva is a convenient biological fluid for disease diagnosis and multi-sampling studies.
• Salivary steroids offer insights into free plasma levels.
• Increased incidence of primary aldosteronism (PA) drives interest in aldosterone measurement.

Purpose of the Study:

• To validate a time-resolved fluorescence immunoassay (TR-FIA) for salivary aldosterone (SA) measurement.
• To assess the utility of SA in diagnosing PA and monitoring aldosterone dynamics.

Main Methods:

• Developed a biotinylated-aldosterone tracer and used a commercial antibody for SA measurement via TR-FIA.
• Collected saliva samples using multi-sampling protocols, including diurnal rhythm, ACTH stimulation, and posture tests.
• Validated the assay for sensitivity and precision, and compared SA with plasma aldosterone measurements.

Main Results:

• The SA assay demonstrated a sensitivity of 19 ng/L with good intra-/inter-assay precision.
• Salivary aldosterone (SA) showed significant correlation with plasma aldosterone (r(2)=0.60).
• SA levels were significantly higher in PA patients (111 ng/L) compared to healthy subjects (50 ng/L), and showed gender-dependent responses to posture changes.

Conclusions:

• Salivary aldosterone (SA) measurement is a reliable and convenient method for assessing plasma aldosterone levels and dynamic responses.
• SA is a valuable biomarker for diagnosing primary aldosteronism (PA).
• The study identified gender-specific aldosterone responses to postural changes, highlighting the utility of SA in multi-sampling studies.