An update on FIV and FeLV test performance using a Bayesian statistical approach.
BACKGROUND
Screening tests for feline retroviruses are thought to have high sensitivity and specificity, although previous studies that evaluated these tests have limitations. Novel statistical approaches have been developed that allow the estimation of sensitivity and specificity in situations where the true state of the disease in individual animals cannot be assured.


OBJECTIVE
The purpose of this study was to evaluate the sensitivity and specificity of a variety of retrovirus tests, including some screening tests, in a population of cats potentially infected with either feline leukemia virus (FeLV) and/or feline immunodeficiency virus (FIV) by using a Bayesian statistical approach.


METHODS
Four hundred and ninety blood samples from cats being evaluated for FIV infection were tested by 2 rapid immunomigration tests (Witness single [WS], Witness combi [WC]) and a plate-based ELISA (Petcheck) for FIV antibody, and by a newly designed real-time polymerase chain reaction (PCR) assay for FIV provirus. Four hundred and ninety-five blood samples from cats being evaluated for FeLV infection were tested by 2 rapid immunomigration tests (WS, WC) and a plate-based ELISA (Petcheck) for FeLV antigen, and by a FeLV virus isolation technique. Results were then analyzed by using a Bayesian statistical method.


RESULTS
For FIV tests, median sensitivity estimates were 0.98 for WS, 0.97 for WC, 0.98 for ELISA, and 0.92 for PCR. Median specificity estimates were 0.96 for WS, 0.96 for WC, 0.93 for ELISA, and 0.99 for PCR. For FeLV tests, median sensitivity estimates were 0.97 for WS, 0.97 for WC, 0.98 for ELISA, and 0.91 for virus isolation. Median specificity estimates were 0.96 for WS, 0.96 for WC, 0.98 for ELISA, and 0.99 for virus isolation.


CONCLUSIONS
The use of Bayesian statistical methods overcomes a variety of methodologic problems associated with diagnostic test evaluations, including the lack of a definitive reference test. The sensitivity and the specificity of all 6 evaluated screening tests was high: however, specificity estimates were slightly lower than those reported by most recent studies.
Pinches
Mark D G
MD
Department of Clinical Veterinary Science, University of Bristol, UK. mark.pinches@wcdx.co.uk
Diesel
Gillian
G
Helps
Christopher R
CR
Tasker
Séverine
S
Egan
Kathy
K
Gruffydd-Jones
Tim J
TJ
D000818:Animals; D001499:Bayes Theorem; D002371:Cat Diseases / Q000175:diagnosis* / Q000821:virology; D002415:Cats; D003955:Diagnostic Tests, Routine / Q000379:methods / Q000592:standards / Q000662:veterinary*; D016089:Immunodeficiency Virus, Feline / Q000302:isolation & purification*; D016180:Lentivirus Infections / Q000175:diagnosis / Q000662:veterinary*; D005256:Leukemia Virus, Feline / Q000302:isolation & purification*; D012192:Retroviridae Infections / Q000175:diagnosis / Q000662:veterinary*; D012680:Sensitivity and Specificity; D013045:Species Specificity; D014412:Tumor Virus Infections / Q000175:diagnosis / Q000662:veterinary*