Sensitivity, specificity, and predictive values of ClinEase-Virastat saliva test for feline leukemia virus infection

Detection of virus in saliva using a commercial enzyme-linked immunosorbent assay (ELISA), ClinEase-VirastatR, was compared to evidence of FeLV infection by the indirect immunofluorescent antibody assay (IFA) and plasma ELISA. The sensitivity and specificity of the saliva ELISA were derived by comparison to IFA and plasma ELISA in 103 cats from a large colony in New York State. The sensitivity of the saliva test in relation to IFA and plasma ELISA was approximately 100% and 93%, respectively. The specificity of the saliva ELISA in relation to IFA and plasma ELISA was approximately 85% and 92%, respectively. This test appears to be particularly suitable as a screening test for FeLV infection, especially in populations where the expected prevalence is low. Because of its high sensitivity, the saliva test has a high negative predictive value, particularly in populations where the disease is rare. Since the specificity is moderate, however, the predictive value of a positive test will be poorest in cats originating from places where the infection is rare (e.g. single cat households, or free roaming cats), and better among cats from environments having a high prevalence of FeLV (e.g. multiple-cat households).