# Establishment and Validation of Sensitive Liquid Chromatography–Tandem Mass Spectrometry Method for Aldosterone Quantification in Feline Serum with Reference Interval Determination

## TL;DR

This study developed a precise method to measure aldosterone in cat blood and set a reference range for healthy cats, aiding in diagnosing related health issues.

## Contribution

A validated LC-MS/MS method for feline aldosterone quantification with a reference interval for healthy cats is established.

## Key findings

- The method has a limit of quantification of 5 pg/mL and inter-assay variation under 15%.
- The reference interval for healthy cats is 5.0–78.4 pg/mL (13.8–217.2 pmol/L).
- The method supports diagnosing and monitoring aldosterone-related disorders in cats.

## Abstract

Aldosterone is a crucial mineralocorticoid hormone in small animals, particularly cats, as imbalances can contribute to conditions like arterial hypertension, hypokalaemia, and chronic kidney disease. This study introduces a validated liquid chromatography–tandem mass spectrometry method for precise serum aldosterone measurement in cats, with a limit of quantification of 5 pg/mL. The method established a reference interval of 5.0–78.4 pg/mL (13.8–217.2 pmol/L) for healthy cats, providing a reliable tool for diagnosing and monitoring aldosterone-related disorders in veterinary practice.

Aldosterone, a mineralocorticoid hormone synthesised in the adrenal cortex, is essential for maintaining electrolyte balance and fluid homeostasis. Its role in feline physiology remains underexplored, despite its importance in regulating sodium reabsorption and potassium excretion via mineralocorticoid receptors in renal tubules. This study is warranted given aldosterone’s importance in cats, particularly in light of their unique physiological traits, including highly concentrated urine and sensitivity to hydration status. Primary hyperaldosteronism, the most common feline adrenocortical disorder, contributes to arterial hypertension and chronic kidney disease, yet often remains underdiagnosed due to overlapping symptoms like hypokalaemia and hypertension. This research aimed to validate a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method to measure serum aldosterone and to establish a reference interval in a population of healthy cats across a broad age range. The method demonstrated high precision and accuracy, with inter-assay coefficients of variation under 15%. Analysis of 49 healthy cats (40 young, 9 old) revealed a reference interval of 5.0–78.4 pg/mL (13.8–217.2 pmol/L). These findings provide a robust framework for diagnosing aldosterone-related disorders in cats and underscore the need for species-specific diagnostic tools. Improved understanding of aldosterone’s role could refine treatment strategies and enhance outcomes for affected feline patients.