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Effect of pH and storage conditions on measured ionised calcium concentration in dogs and cats
Michal Mazaki-Tovi1, Shira Topol2, Itamar Aroch2
1Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel michal.tovi@mail.huji.ac.il.
Insights
Aerobic sample handling decreases ionized calcium (iCa) levels in dogs and cats. Correction formulas based on pH can accurately adjust measured iCa concentrations for stored samples.
Area of Science:
- Veterinary Clinical Pathology
- Biochemistry
- Analytical Chemistry
Background:
- Aerobic blood sample handling increases serum pH, leading to decreased ionized calcium (iCa) levels.
- Accurate iCa measurement is crucial for diagnosing various health conditions in animals.
Purpose of the Study:
- To investigate the impact of pH and storage conditions on serum iCa measurements in dogs and cats.
- To develop correction formulas for iCa concentrations in aerobically collected samples.
Main Methods:
- Prospective study involving blood samples from 44 dogs and 25 cats.
- Immediate measurement of iCa and pH under anaerobic conditions.
- Comparison with iCa measurements from samples stored under various aerobic conditions.
Main Results:
- Significantly lower iCa concentrations were observed in aerobically stored samples compared to anaerobically handled samples in both species (P<0.01).
- The most substantial decrease in iCa was noted after storage at -20°C for 30 days.
- Developed correction formulas (corrected iCa = measured iCa + coefficient × (measured pH - 7.41)) showed good agreement between corrected and actual iCa values.
Conclusions:
- Serum samples for iCa measurement can be stored at 4°C or -20°C for up to 24 hours.
- For extended storage periods, -80°C is recommended to maintain iCa stability.
- The established correction formulas enable accurate iCa determination from aerobically handled samples.
Background:
Aerobic blood sample collection and processing results in increased serum pH and decreased ionised calcium (iCa) concentration. This prospective study aimed to determine the effect of pH and storage conditions on measured iCa concentration in serum samples obtained from dogs and cats and establish correction formulas for use in samples obtained aerobically.
Methods:
Blood samples were collected from 44 dogs and 25 cats; iCa and pH were measured immediately under anaerobic conditions and in samples stored under several aerobic conditions.
Results:
Measured iCa concentrations were significantly lower in samples stored at all aerobic conditions than in samples handled anaerobically in both dogs and cats (P<0.01 for all). The largest and most clinically significant differences were noted in samples stored at -20°C for 30 days in both dogs (0.48 mmol/l; 95 per cent CI 0.40 to 0.55) and cats (0.40 mmol/l; 95 per cent CI 0.33 to 0.47). Correction formulas (corrected iCa=measured iCa+coefficient × (measured pH-7.41); coefficient=0.597 for dogs, 0.627 for cats) yielded good agreement between the corrected and the actual iCa concentrations.
Conclusions:
Samples for iCa measurement can be stored at either 4°C or -20°C for 24 hours. Storage at -80°C is recommended for longer storage time periods.
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