Evaluation of five commercially available assays and measurement of serum total protein concentration via refractometry for the diagnosis of failure of passive transfer of immunity in foals.
OBJECTIVE
To determine and compare sensitivity, specificity, accuracy, and predictive values of measurement of serum total protein concentration by refractometry as well as 5 commercially available kits for the diagnosis of failure of passive transfer (FPT) of immunity in foals.


METHODS
Prospective study.


METHODS
65 foals with various medical problems and 35 clinically normal foals.


METHODS
IgG concentration in serum was assessed by use of zinc sulfate turbidity (assay C), glutaraldehyde coagulation (assay D), 2 semiquantitative immunoassays (assays F and G), and a quantitative immunoassay (assay H). Serum total protein concentration was assessed by refractometry. Radial immunodiffusion (assays A and B) was used as the reference method.


RESULTS
For detection of IgG < 400 mg/dL, sensitivity of assay H (100%) was not significantly different from that of assays C, E, and G (88.9%). Specificity of assays H (96.0%) and G (95.8%) was significantly higher than that of assays C (79.4%) and E (78.1 %). For detection of IgG < 800 mg/dL, sensitivities of assays H (976%), D (92.9%), C (81.0%), and G (81.0%) were significantly higher than that of assay F (52.4%). Specificity of assays F (100%), G (94.7%), and H (82.8%) was significantly higher than that of assays C (56.9%) and D (58.6%). Serum total protein concentration < or = 4.5 g/dL was suggestive of FPT, whereas values > or = 6.0 g/dL indicated adequate IgG concentrations.


CONCLUSIONS
Most assays were adequate as initial screening tests. However, their use as a definitive test would result in unnecessary treatment of foals with adequate IgG concentrations.
Davis
Rachel
R
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32610-0136, USA.
Giguère
Steeve
S
D000818:Animals; D000831:Animals, Newborn / Q000097:blood; D001798:Blood Proteins / Q000032:analysis*; D006736:Horses / Q000097:blood / Q000276:immunology*; D007112:Immunity, Maternally-Acquired; D007118:Immunoassay / Q000379:methods / Q000662:veterinary; D007074:Immunoglobulin G / Q000032:analysis / Q000097:blood*; D009391:Nephelometry and Turbidimetry / Q000379:methods / Q000662:veterinary; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012016:Reference Values; D012031:Refractometry / Q000379:methods / Q000662:veterinary*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D001798:Blood Proteins; D007074:Immunoglobulin G