Sensitivity and specificity of serum copper determination for detection of copper deficiency in feeder calves.
OBJECTIVE
To determine the relationship between serum and liver copper concentrations and evaluate serum copper determination for diagnosis of copper deficiency in juvenile beef calves.


METHODS
Cross-sectional study.


METHODS
105 juvenile beef calves.


METHODS
Copper concentrations were measured in paired liver and serum samples from 6- to 9-month-old beef calves. Regression models that predicted liver copper concentration as a function of serum copper concentration were developed. Sensitivity and specificity of serum copper concentration for detection of low liver copper concentration were determined, using a range of serum copper concentrations as test endpoints. Positive and negative predictive values were calculated.


RESULTS
The association between serum and liver copper concentrations was significant; however, regression models accounted for only a small portion of the variation in liver copper concentrations. For a serum copper concentration endpoint of 0.45 microg/g, sensitivity and specificity for detection of low liver copper concentration were 0.53 and 0.89, respectively. Positive and negative predictive values of serum copper concentration for detection of low liver copper concentration ranged from 0.37 to 0.85 and 0.63 to 0.94, respectively.


CONCLUSIONS
Regression models are inappropriate for predicting copper status as a function of serum copper concentration. Serum copper concentration is fairly specific for detection of low liver copper concentration but only marginally sensitive when serum copper concentration of 0.45 microg/g is used as a test endpoint. The value of serum copper concentration as a diagnostic indicator depends on prevalence of copper deficiency.
Department of Veterinary Medicine, University of Missouri, Columbia 65202, USA.
R K
RK
Tessman
J
J
Lakritz
J W
JW
Tyler
S W
SW
Casteel
J E
JE
Williams
R K
RK
Dew
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000175:diagnosis*; D003300:Copper / Q000097:blood* / Q000172:deficiency*; D003430:Cross-Sectional Studies; D008099:Liver / Q000378:metabolism*; D015233:Models, Statistical; D012044:Regression Analysis; D012680:Sensitivity and Specificity
D003300:Copper