Evaluation of an immunoassay for determination of haptoglobin concentration in various biological specimens from swine.

OBJECTIVE: To develop and evaluate an immunoassay based on time-resolved immunofluorometry (TR-IFM) for measurement of haptoglobin concentrations in samples of various body fluids of swine. ANIMALS: 20 pigs without clinical signs of disease and seronegative for antibodies against major viruses that affect pigs and 30 pigs with clinical signs of disease. PROCEDURES: Haptoglobin concentrations were measured in samples of serum, saliva, and meat juice obtained from both groups of pigs to evaluate the ability of TR-IFM to differentiate between healthy and diseased pigs. Performance of TR-IFM was evaluated by means of its calibration curve and detection limit, analytic precision during routine operation, and linearity of results for serial dilutions for the 3 types of samples. In addition, performance of TR-IFM was compared with that of a commercial spectrophotometric assay.
RESULTS: The TR-IFM assay involved only 1 step, and the results were obtained in 20 minutes, with good analytic sensitivity and reproducibility. The analytic limit of detection was 0.52 ng/mL. Intra-assay and interassay coefficients of variation ranged from 1.13% to 4.81% and 5.97% to 13.57%, respectively. The method yielded linear results for all sample types. Serum haptoglobin concentrations determined by use of TR-IFM and spectrophotometric assays were highly correlated (r = 0.96). Differences between healthy and diseased pigs with respect to median haptoglobin concentrations were significant for all types of samples. CONCLUSIONS AND CLINICAL RELEVANCE: The 1-step TR-IFM assay accurately quantified haptoglobin concentrations in serum, saliva, and meat juice samples from swine and may be useful in laboratory and meat inspection settings.