Serum calcium determination with atomic absorption spectrophotometry and colorimetric method: association and predictive

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ORIGINAL ARTICLE

Serum calcium determination with atomic absorption spectrophotometry and colorimetric method: association and predictive equations between them in cattle and sheep samples P. D. Katsoulos 1

&

L. V. Athanasiou 2

&

A. Dedousi 3

&

Z. S. Polizopoulou 4

Received: 6 July 2020 / Accepted: 5 November 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020

Abstract The objectives of the present study were to compare the serum calcium (Ca) concentrations in cattle and sheep measured by the flame atomic absorption spectrophotometry (AAS) and those obtained with a colorimetric method (CM) and to generate equations that allow their prediction. Serum Ca concentration was determined in 50 dairy cattle and 50 dairy sheep nonhemolyzed blood samples with AAS and CM. The data were analyzed with paired sample t test and Bland–Altman plots were generated. Using a random number generator, 25 samples from each species were selected to create predictive equations between the two methods using Passing-Bablok regression analysis. The predictive equations were validated at the remaining 25 samples for each species using Bland–Altman plots. The average bias between the two methods was 5.5% for cattle and 18.1% for sheep samples. Mean Ca values determined with CM were significantly lower than those measured with AAS (P < 0.05) in both species. The use of the generated equations y = 0.706 + 0.727x for cattle and y = 0.744 + 0.833x for sheep (mmol/l) allows the prediction of AAS determined Ca (y) using CM determined Ca values (x) with average bias 1.8% for cattle and 1.9% for sheep. The two methods for calcium determination evaluated cannot be used interchangeably and the respective reference intervals and cut-off values should be taken into account to make clinical decisions in cattle and sheep. The use of the proposed equation for cattle is considered as acceptable for the calculation of bias corrected reference ranges and cut-off values. Keywords Atomic absorption spectrophotometry . Calcium . Cattle . Colorimetric Method . Sheep

Introduction Hypocalcemia, clinical or subclinical, is considered as the most important metabolic disorder in dairy cattle at the periparturient period. Apart from milk fever, the clinical form of hypocalcemia that occurs on or soon after calving and can

* P. D. Katsoulos [email protected] 1

Clinic of Farm Animals, School of Veterinary Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece

2

Clinic of Medicine, Faculty of Veterinary Medicine, School of Health Sciences, University of Thessaly, Karditsa, Greece

3

Veterinary Research Institute, HAO – Demeter, Thessaloniki, Greece

4

Diagnostic Laboratory, School of Veterinary Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece

be life threatening, subclinical hypocalcemia increases the risk for other metabolic and infectious disorders (Goff 2008). It is now well documented that subclinical hypocalcemia predisposes the cow for health issues such as negative energy balance and ketosis (Reinhardt