Acidification is required for calcium and magnesium concentration measurements in equine urine.
Authors: Lapsina Sandra, Stirn Martina, Hofmann-Lehmann Regina, Schoster Angelika, Riond Barbara
Journal: BMC veterinary research
Summary
# Editorial Summary Accurate measurement of urinary calcium, magnesium and phosphate concentrations in horses requires careful attention to sample preparation, as these minerals exist in multiple chemical forms that affect analytical results. Researchers analysed 32 equine urine samples across four years, measuring electrolyte concentrations and fractional excretion values under three conditions: native urine, urine acidified immediately to pH 1–2 with hydrochloric acid, and urine measured one hour after acidification, whilst also collecting paired blood samples for comparative analysis. Acidification significantly increased measured calcium and magnesium concentrations compared to unacidified native urine, reflecting the dissociation of ion complexes that would otherwise be undetectable by standard laboratory methods, though phosphate concentrations and fractional excretion calculations remained stable across conditions. Storage time after acidification did not materially alter results, indicating that immediate analysis is not essential once samples have been properly treated. For equine practitioners and clinicians interpreting urinary electrolyte results—whether assessing renal function, identifying mineralisation disorders or evaluating dietary adequacy—these findings confirm that acidification is a mandatory pre-analytical step rather than optional practice, and that results from non-acidified samples will significantly underestimate true mineral excretion and should not be relied upon for clinical decision-making.
Read the full abstract on PubMed
Practical Takeaways
- •Always acidify urine samples to pH 1-2 before submitting for calcium and magnesium analysis to ensure accurate results for clinical decision-making
- •Samples can be safely stored after acidification without significant degradation, allowing flexibility in sample handling and submission timing
- •Ensure your laboratory acidifies samples appropriately when ordering equine urine electrolyte panels, or pre-treat samples yourself if performing in-house analysis
Key Findings
- •Acidification of equine urine is required to accurately measure calcium and magnesium concentrations due to dissociation of ion complexes
- •Storage time after acidification (immediate vs 1 hour post-acidification) does not significantly affect measured electrolyte concentrations
- •Fractional excretion calculations for calcium, magnesium and phosphate are dependent on proper urine acidification protocols