Relationship between haptoglobin, serum amyloid A, and clinical status in a survey of dairy herds during a 6-month period

Background: Haptoglobin and serum amyloid A are major acute phase proteins in cattle. Dairy cattle often develop pathologic conditions in the peripartum period; acute phase proteins may be useful in their diagnosis. Objectives: The purpose of this study was to compare the accuracy of serum haptoglobin (Hp) and serum amyloid A (SAA) concentrations with clinical health status for diagnosing disease during the peripartum period in dairy cattle. Methods: Dairy cows from 4 herds were evaluated every 15 days over a 6-month period. Health status was determined by thorough clinical examination. Haptoglobin and SAA concentrations were measured in serum using validated methods and the results were classifed as positive or negative based on defined cutoff points. Disease prevalence, sensitivity, and specificity were compared using clinical examination as the gold standard. Results: A total of 1896 samples from 158 cows were analyzed. Significant increases in mean Hp and SAA concentrations were observed in the week following parturition in both primiparous and multiparous cows, although high interindividual variability was observed. Both Hp and SAA had low sensitivity but higher specificity in determining disease status compared with clinical examination. Increased concentrations of Hp and SAA were found in < 10% of samples from clinically healthy cows, except in the week after parturition. Conclusions: Haptoglobin and serum amyloid A should be used with caution as markers of inflammation in the week after calving. Poor sensitivity in other postpartum periods could be related to the higher incidence of chronic (vs acute) inflammation. Haptoglobin may be appropriate for routine screening, but further work needs to be done to assess its value as an indicator of herd health.