Evaluation of a competitive immunoassay for the detection of bovine haptoglobin

A competitive immunoassay to quantify the serum concentration of bovine haptoglobin (hp) using time resolved fluorescence was compared with an indirect method of hp assay (haemoglobin binding assay), using sera taken from healthy animals (n = 158), animals experimentally infected with Haemophilus somnus (n = 10) and from sick animals requiring veterinary treatment (n = 440). Upper limits of normality (for normal animals) were tentatively established for the immunoassay (2.1 micrograms ml-1) and for the haemoglobin binding assay (103 micrograms ml-1). The competitive immunoassay detected elevated hp in 62.5 per cent of field sera by comparison with only 19.2 per cent using the conventional haemoglobin binding assay. Serum albumin concentration did not correlate with hp although concentrations of globulins and copper did correlate. However, these parameters (serum globulin and copper) were found to be insensitive markers of inflammatory disease.