Sensitivity and specificity of serum copper determination for detection ofcopper deficiency in feeder calves

Objective - To determine the relationship between serum and liver copper co ncentrations and evaluate serum copper determination for diagnosis of coppe r deficiency in juvenile beef calves. Design - Cross-sectional study. Animals - 105 juvenile beef calves. Procedure - Copper concentrations were measured in paired liver and serum s amples from 6- to 9-month-old beef calves. Regression models that predicted liver copper concentration as a function of serum copper concentration wer e 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 pre dictive 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 concen tration endpoint of 0.45 ug/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 fo r predicting copper status as a function of serum copper concentration. Ser um copper concentration is fairly specific for detection of low liver coppe r concentration but only marginally sensitive when serum copper concentrati on of 0.45 ug/g is used as a test endpoint. The value of serum copper conce ntration as a diagnostic indicator depends on prevalence of copper deficien cy.