Sensitivity and specificity of blood test kits for feline leukemia virus antigen

Enzyme-linked immunosorbent assay (ELISA) test kits have been used widely to diagnose FeLV infection. Several companies have licensed such kits, but because these test kits are designed somewhat differently, a demonstration of their relative merits was needed. Differences in the sensitivity and specificity of 7 commercial test kits were determined by testing sera that induce false-negative (limiting dilution of FeLV group specific antigen, p27), and false-positive (cat anti-mouse antibody) test results. Among the panels of sera used in this study, significant differences in test kit sensitivity were not observed, but differences in specificity were identified. An interim report of these studies, supplied to the manufacturers, prompted changes in some of the kits, resulting in improved specificities. Generally, FeLV test kits are now more efficient in accurately detecting p27 in blood, serum, or plasma of cats. Nevertheless, some kits still lack specificity attributable to reagents supplied by the manufacturer.