Use of a water hardness test kit to measure serum calcium concentration in cattle.
OBJECTIVE
To determine whether a commercially available water hardness test kit could be used to measure total serum calcium concentration and diagnose hypocalcemia in dairy cows.


METHODS
Prospective study.


METHODS
30 dairy cows from 19 commercial herds.


METHODS
Serum calcium concentration was determined using a water hardness test kit and a standard, laboratory-based method. Simple linear regression was used to determine whether there was a linear relationship between results of the 2 methods, and Spearman's rank correlation was used to calculate correlation between measurements. Sensitivity, specificity, and predictive values of using test kit-derived values for diagnosis of hypocalcemia (laboratory value < 8 mg/dl) were calculated.


RESULTS
There was a high correlation and significant linear relationship between results of the 2 methods. Sensitivity, specificity, predictive value of a positive test result, and predictive value of a negative test result were 100, 73, 86, and 100%, respectively. Accuracy was improved by using a test kit-derived calcium concentration of 7 mg/dl as the cut-off for determining hypocalcemia.


CONCLUSIONS
Results indicate that a commercially available water hardness test kit can be used as a rapid, inexpensive method of estimating serum calcium concentrations and diagnosing hypocalcemia in dairy cattle. However, the test is not practical for cow-side use, because blood samples must be centrifuged to obtain serum for use in the test kit.
Matsas
D J
DJ
Department of Clinical Sciences, New York State College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401, USA.
Warnick
L D
LD
Mechor
G D
GD
Seib
L N
LN
Fatone
S
S
White
M E
ME
Guard
C L
CL
D000818:Animals; D001774:Blood Chemical Analysis / Q000191:economics / Q000592:standards / Q000662:veterinary; D002118:Calcium / Q000097:blood*; D002417:Cattle / Q000097:blood*; D005260:Female; D016014:Linear Models; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic / Q000191:economics / Q000592:standards / Q000662:veterinary; D012680:Sensitivity and Specificity; D014867:Water / Q000737:chemistry
D011933:Reagent Kits, Diagnostic; D014867:Water; D002118:Calcium