Work

Formulae to correct sodium concentrations for serum water fraction in cases of hypo‐ and hyperproteinemia in dogs

Year: 2025

Type: article

Abstract: Background Biochemistry analyzers, which utilize indirect potentiometry, are used to determine serum electrolyte concentrations in dogs. Artifactual increases or decreases in these electrolyte concentrations can be caused by alterations in the serum water fraction (SWF). Severe hypo‐ and hyperproteinemia cause changes in SWF, which can then result in incorrectly reported serum sodium concentrations. Objectives The goals of this study were to determine an average actual SWF (SWFACTUAL) in dogs and establish formulae to correct serum sodium concentration measured by indirect potentiometry in hypo‐ and hyperproteinemic patients. Methods Serum samples from 115 canine patients were analyzed for electrolytes measured by both indirect and direct potentiometry. Total protein, albumin, triglycerides, and cholesterol were also determined. Each serum sample was then lyophilized to determine SWFACTUAL. A canine‐specific formula to estimate SWF (SWFEST‐CAN) was developed using a multivariable linear model and compared with the human‐estimated formula (SWFEST‐HUM). Results The mean SWFACTUAL in this population of dogs was 92.7%, which was significantly different (p < .0001) than the mean (95.1%) calculated using SWFEST‐HUM. The formula derived from SWFEST‐CAN recapitulated SWFACTUAL more accurately than SWFEST‐HUM. Based on a slope closer to 1.0, the corrected sodium concentrations calculated using the canine formula correlated marginally better with the serum sodium measured by direct potentiometry than those calculated using the human formula. Conclusions Applications of correction formulae are expected to limit the misinterpretation of electrolyte data from indirect potentiometry when altered SWF occurs. A case example of the potential utility of these correction formulae is presented.

Source: Veterinary Clinical Pathology

DOI: 10.1111/vcp.13410