Tessman RK, Lakritz J, Tyler JW, Casteel SW, Williams JE, Dew RK. Sensitivity and specificity of serum copper determination for detection of copper deficiency in feeder calves.
J Am Vet Med Assoc 2001;
218:756-60. [PMID:
11280412 DOI:
10.2460/javma.2001.218.756]
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Abstract
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.
DESIGN
Cross-sectional study.
ANIMALS
105 juvenile beef calves.
PROCEDURE
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 AND CLINICAL RELEVANCE
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.
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