Comparison of turbidometric immunoassay, refractometry, and gamma-glutamyl transferase to radial immunodiffusion for assessment of transfer of passive immunity in high-risk beef calves
Abstract
BACKGROUND: Attainment of adequate transfer of passive immunity (TPI) is critical to health of calves; however, studies comparing available tools for measurement of TPI in individual beef animals are limited.
OBJECTIVES: To report agreement between 4 tests evaluating individual TPI status in beef calves.
ANIMALS: One hundred ninety-six beef calves born to cows and heifers presenting for calving management or dystocia.
METHODS: Retrospective study to assess serum immunoglobulin (IgG) concentrations via turbidimetric immunoassay (TI), gamma-glutamyl transferase (GGT), serum total protein (TP), and single radial immunodiffusion (RID; reference standard). Test agreement was evaluated using Passing-Bablok regression, Bland-Altman analysis, Cohen's kappa, and receiver operating characteristic (ROC) curves with and without covariate adjustment to determine optimal thresholds.
RESULTS: Correlation between RID and test results varied: TI, ρ = 0.757; TP, ρ = 0.715; GGT: ρ = 0.413. For the TI compared to RID, regression analysis identified a constant (intercept = -0.51 [CI: -2.63, 3.05]) and proportional (slope = 1.87 [CI: 1.69, 2.08]) bias. Based on ROC, TI concentrations of ≤9.89 and ≤13.76 g/L, and TP concentrations of ≤5.5 and ≤6.0 g/dL, indicated IgG concentrations <18.0 and <25.0 g/L, respectively.
CONCLUSIONS AND CLINICAL IMPORTANCE: Within this cohort of calves, TI demonstrated the best correlation with RID; however, significant bias was identified which led to frequent…
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Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence.
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