Performance characteristics and optimisation of cut-off values of two enzyme-linked immunosorbent assays for the detection of antibodies to Neospora caninum in the serum of cattle.
OBJECTIVE
To determine the performance characteristics of two enzyme-linked immunosorbent assays (ELISAs) manufactured by Institut Pourquier (IP) for the detection of antibodies against Neospora caninum in bovine sera.


METHODS
Sera from 526 cattle were assayed in two ELISAs (IP) for the detection of anti-N. caninum antibodies. Results from a further ELISA (IDEXX) were used to provide the "gold standard"N. caninum infection status of the cattle and the ELISA results assessed by two-graph receiver operating characteristic (TG-ROC) analysis.


RESULTS
TG-ROC analysis suggested changes to one of the IP ELISA protocols, arriving at a cut-off threshold that was different to the one recommended by the manufacturer. With that change, both of the ELISAs performed with high sensitivity and specificity (in excess of 98%) for bovine sera.


CONCLUSIONS
The analysis of the two IP ELISAs when used on individual bovine sera demonstrated high sensitivity and specificity. TG-ROC analyses optimised the cut-off point suggested by the manufacturer for one of these commercial diagnostic assays and found agreement with the manufacturer's cut-off regarding the other assay. This will help with the accurate identification of infected animals and thereby contributing to the control of neosporosis.
Hall
C A
CA
Novartis Animal Health Australasia Pty Ltd., Yarrandoo R&D Centre, 245 Western Rd., Kemps Creek, NSW 2178, Australia. craig.hall@novartis.com
Reichel
M P
MP
Ellis
J T
JT