Detection of FeLV antigen by indirect immunofluorescence in ELISA/CITE negative cats
Kerr, M.G.; Smith, K.J.
Veterinary Record 136(20): 516-518
1995
ISSN/ISBN: 0042-4900 PMID: 7660550 Document Number: 445876
Blood samples from 149 cats submitted during September to November 1993, were investigated for feline leukaemia (FeLV) antigen using both ELISA and immunofluorescent antibody (IFA) testing. 118 cats had a clinical or haematological reason to suspect FeLV involvement, 31 were healthy cats. 48 cats were positive for FeLV in one or both tests with 16 cats positive for FeLV using ELISA and 46 using IFA; only 14 were positive by both methods. 19 of the sick cats who had been tested previously using a CITE kit with negative results, all gave negative results by ELISA but 13 were positive by IFA including 7 with actual leukaemia. Pleural fluid samples from 6 other cats were also examined by IFA; 5 in which thymic lymphosarcoma had been diagnosed cytologically were positive, the sixth sample which had been diagnosed cytologically as a pyothorax was negative. Although it is not possible to estimate the incidence of false negative ELISA reactors from the results it is clear that they occur frequently enough to be of practical diagnostic concern.