Validation of a commercially available cELISA test for canine neosporosis against an indirect fluorescent antibody test (IFAT)

A commercially available competitive enzyme-linked immunosorbent assay (cELISA, VMRD^®) was validated for the detection of Neospora caninum antibodies in the serum of dogs, using as a reference test an indirect fluorescent antibody test (IFAT, Fuller^®). A partial verification approach was used. A total of 618 dogs were screened with cELISA and a subset of positive and negative sera (n = 237) were then tested with IFAT. Naïve relative sensitivity (SE_nv) and naïve relative specificity (SP_nv) of cELISA were calculated and then corrected (SE_corr; SP_corr) for studies with partial validation. Results showed a SE_nv of 72% and a SP_nv of 89.3%; corrected estimates showed a SE_corr of 47% and a SP_corr of 96%. ROC analysis showed that the cutoff recommended by the manufacturer (30%) corresponded to the highest naïve sensitivity (72%) combined with a good naïve specificity (90%) of cELISA. Corrected estimates of SE and SP for partial verification method revealed that SE of the cELISA is lower and SP is higher than naïve estimates. The results suggest to use this test for confirmation of a clinical suspicion of neosporosis, and to use some techniques for adjustment of misclassification in prevalence and risk-factor studies.