A comparison of serum and plasma cytokine values using a multiplexed assay in cats

BackgroundDegenerative joint disease (DJD) is highly prevalent in cats, and pain contributes to morbidity. In humans, alterations of cytokine concentrations have been associated with joint deterioration and pain. Similar changes have not been investigated in cats. Cytokine concentrations can be measured using multiplex technology with small samples of serum or plasma, however, serum and plasma are not interchangeable for most bioassays. Correlations for cytokine concentrations between serum and plasma have not been evaluated in cats.ObjectiveTo evaluate the levels of detection and agreement between serum and plasma samples in cats.AnimalsPaired serum and plasma samples obtained from 38 cats.MethodsBlood was collected into anti-coagulant free and EDTA Vacutainer® tubes, serum or plasma extracted, and samples frozen at −80 °C until testing. Duplicate samples were tested using a 19-plex feline cytokine/chemokine magnetic bead panel.ResultsAgreement between serum and plasma for many analytes was high, however correlation coefficients ranged from −0.01 to 0.97. Results from >50% of samples were below the lower limit of quantification for both serum and plasma for nine analytes, and for an additional three analytes for plasma only.Conclusions and clinical importanceWhile serum and plasma agreement was generally good, detection was improved using serum samples.