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Veterinary clinical pathology2023; 52(2); 252-260; doi: 10.1111/vcp.13200

Sample stability and heparin interference in ionized calcium and ionized magnesium measurements in horses using the Stat Profile Prime Plus co-oximetry electrolyte analyzer.

Abstract: The determination of iCa and iMg is important in veterinary medicine, but their immediate determination in whole blood is not always possible. Their stability in other sample types and the existence of interferences must be evaluated before its use. Objective: We aimed to analyze the effects of storage time on the stability of iCa, iMg, and other analytes in whole blood, plasma, and serum samples in horses and assess the interference of heparin in these measurements. Methods: Whole blood, heparin-plasma, and serum samples from 10 horses were stored at 4°C and analyzed 1, 2, 3, 4, 5, 6, 7, 8, 24, 48, and 168 hours after sample collection using the Stat Profile Prime Plus Vet equipment (Nova Biomedical, Waltham, MA, USA). Results were analyzed by ANOVA or mixed-effect models. Results: The concentration of iCa, iMg, total calcium (tCa), total magnesium (tMg), and the ratios iCa/tCa and iMg/tMg did not differ up to 168 hours when compared to the initial time. Total Ca, iMg, and tMg were not significantly different among sample types, but iCa concentrations were slightly but significantly lower in plasma. Freezing at -20°C did not affect iCa, iMg, tCa, and tMg. The pH increased in serum and plasma after 8 hours, and a mild negative correlation existed between plasma iCa concentration and pH. A negative correlation was observed also between the ratios iCa/tCa or iMg/tMg and pH in plasma and serum. A significant decrease in iCa and iMg was detected when comparing homemade syringes at high heparin concentration (~200-300 U heparin/mL) and commercial lithium-heparin tubes (20-30 U/mL). Conclusions: Samples stored at 4°C can be used to determine iCa and iMg concentrations up to 7 days after collection. Other metabolites are stable for up to 8 hours; heparin interference should be taken into account if using homemade heparin syringes.
© 2023 The Authors. Veterinary Clinical Pathology published by Wiley Periodicals LLC on behalf of American Society for Veterinary Clinical Pathology.
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Publication Date: 2023-02-06 PubMed ID: 36746672DOI: 10.1111/vcp.13200Google Scholar: Lookup
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Summary

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The research sought to investigate the stability of ionized calcium (iCa) and ionized magnesium (iMg) in blood samples from horses over time and explore any interference caused by the use of heparin, particularly in homemade syringes. The outcomes were that samples stored at 4°C can still yield accurate concentrations of iCa and iMg for up to seven days after collection, and high concentrations of heparin could interfere with the results.

Objective and Methodology

  • This study was aimed at exploring the impacts of storage time on the stability of iCa, iMg, and other analytes in different kinds of horse blood samples – whole blood, plasma, and serum. In addition, the influence of heparin on these measurements was evaluated.
  • For the study, whole blood, serum, and heparin-plasma samples were obtained from ten horses and stored at a cool temperature of 4°C.
  • The samples were then analyzed at various intervals after collection, ranging from 1 hour to a week (168 hours), using the Stat Profile Prime Plus Vet equipment.
  • The results were processed using statistical methods, including ANOVA or mixed-effect models.

Results of the Study

  • According to the research results, the concentrations of iCa and iMg, as well as total calcium (tCa) and total magnesium (tMg), remained consistent up to 168 hours when compared to the initial time.
  • While the concentrations of tCa, iMg, and tMg were similar across all sample types, the concentration of iCa was found to be slightly, yet significantly, lower in plasma samples.
  • The freezing temperature of -20°C did not have any impact on the levels of iCa, iMg, tCa, and tMg.
  • The pH value in serum and plasma samples started increasing after eight hours. A mild negative correlation was observed between the concentration of iCa in plasma and its pH value. This correlation was also noticed between the ratios of iCa/tCa or iMg/tMg and pH in plasma and serum samples.
  • There was a significant reduction in iCa and iMg when high heparin concentration (200 to 300 Units/mL) was used in homemade syringes compared to commercial lithium-heparin tubes (20 to 30 Units/mL).

Conclusions from the Study

  • This research concludes that samples stored at a temperature of 4°C can still provide accurate iCa and iMg concentration determinations up to a week (7 days) after being collected.
  • Regarding other metabolites, their stability can be assured for up to 8 hours.
  • However, it is important to consider heparin interference, especially when employing homemade heparin syringes for collection, due to a notable decrease in iCa and iMg in samples collected using these syringes with high heparin concentration.

Cite This Article

APA
Sanmartí J, Robles-Guirado JA, Jose-Cunilleras E, Bassols A. (2023). Sample stability and heparin interference in ionized calcium and ionized magnesium measurements in horses using the Stat Profile Prime Plus co-oximetry electrolyte analyzer. Vet Clin Pathol, 52(2), 252-260. https://doi.org/10.1111/vcp.13200

Publication

Veterinary clinical pathology
ISSN: 1939-165X
NlmUniqueID: 9880575
Country: United States
Language: English
Volume: 52
Issue: 2
Pages: 252-260

Researcher Affiliations

Sanmartí, Júlia
  • Departament de Medicina i Cirurgia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain.
Robles-Guirado, José Angel
  • Departament de Bioquímica i Biologia Molecular, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain.
Jose-Cunilleras, Eduard
  • Departament de Medicina i Cirurgia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain.
Bassols, Anna
  • Departament de Bioquímica i Biologia Molecular, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain.

MeSH Terms

  • Animals
  • Horses
  • Calcium
  • Heparin
  • Magnesium
  • Electrolytes
  • Hydrogen-Ion Concentration
  • Oximetry / veterinary

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Citations

This article has been cited 3 times.
  1. Ruiz KC, Qualhato AF, Albuquerque LFD, Trentin TC, Santos RR, Ruiz CEB, Oviedo GM, Café MB, Botelho AFM, Martins DB. Influence of temperature and storage time on the stability of biochemical parameters in broilers. Poult Sci 2025 Oct;104(10):105568.
    doi: 10.1016/j.psj.2025.105568pubmed: 40737903google scholar: lookup
  2. Satué K, Fazio E, Medica P, Velasco-Martinez MG, Cravana C, Bruschetta G, La Fauci D. The Pivotal Interaction Between Serotonin and Calcium Shifts in Lactating Pregnant Spanish Purebred Mares: The Aging Effect. Vet Sci 2025 Apr 23;12(5).
    doi: 10.3390/vetsci12050398pubmed: 40431491google scholar: lookup
  3. Ab Rahim SN, Nordin N, Wan Omar WFA, Zulkarnain S, Kumar S, Sinha S, Haque M. The Laboratory and Clinical Perspectives of Magnesium Imbalance. Cureus 2023 Dec;15(12):e49835.
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