The SNAP Feline Triple Test provides sensitiveand specific detection of FeLV infection in cats®

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Study shows the Abaxis® VetScan® Feline FeLV/FIV Rapid Test andZoetis Witness® FeLV-FIV Test demonstrate poor sensitivity for FeLV antigen
Introduction

Conclusion

Feline leukemia virus, or FeLV, is a highly contagious virus that isspread primarily via saliva among both domestic and feral cats incasual close contact—this can include sharing food and water aswell as mutual grooming.

The SNAP Feline Triple Test is highly sensitive and specific fordetecting FeLV antigen in cats.

FeLV infection can be a life-threatening condition— approximately
one-third of cats that are infected with FeLV develop progressive
infections and die of an FeLV-related disease within 3 years.1
The American Association of Feline Practitioners (AAFP)
guidelines state that identification and segregation of infectedcats is considered to be the single most effective method for theprevention of new FeLV infection.2
Infected cats are capable of transmitting the virus approximately
21–30 days postexposure. During this initial stage of infection, theconcentration of FeLV antigen is low, twentyfold or more lower
compared to later stages.3 Test sensitivity is a key factor during
this stage because it allows identification of cats early in thecourse of infection and limits transmission of the virus. Poor test
sensitivity could delay supportive care and result in transmission of
the virus to casual-contact naïve cats.
IDEXX Laboratories conducted a study to determine the sensitivity
and specificity of three in-clinic diagnostic tests for FeLV antigen.

Study design
Samples from 137 cats used in this study were random samples
submitted by veterinary clinics to IDEXX Reference Laboratories
and tested for the presence of FeLV antigen. 87 FeLV-positive
samples and 50 FeLV-negative samples were identified
using a PetChek® ELISA, which included both screening andconfirmatory protocols. The performance of the PetChek ELISA
has been validated in several peer-reviewed studies.4–6 An
immunoflourescence assay (IFA) was not used as a reference testin this study because it “yields a high number of false-negative andfalse-positive results…”1 The limitations of IFA in detecting FeLV
have been well-documented.1,2,4,5The samples were then tested using in-clinic tests following
manufacturers’ protocols. The in-clinic tests evaluated in this study
included IDEXX SNAP® Feline Triple® Test, Abaxis® VetScan® Feline
FeLV/FIV Rapid Test and Zoetis Witness® FeLV-FIV Test. Test results
were compared to the PetChek ELISA results for calculation ofsensitivity and specificity.
In-clinic test

Sensitivity

SNAP Feline Triple Test

96.6%

VetScan® Feline FeLV/FIV Rapid Test

71.3%

Witness FeLV-FIV Test

80.5%

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Note: Specificity was greater than or equal to 98% for all tests.

Table 1: Comparative performance of in-clinic FeLV antigen tests• The Zoetis Witness FeLV-FIV Test was found to be less sensitive
for FeLV antigen detection than the SNAP Feline Triple Test.
Almost 1 in 5 positive samples would be missed on the Witness
FeLV-FIV Test.
• The Abaxis VetScan Feline FeLV/FIV Rapid Test was also found tobe less sensitive for FeLV antigen detection than the SNAP FelineTriple Test. Almost 3 in 10 positive samples would be incorrectly
called negative on the VetScan test.
These conclusions are consistent with those presented in an
abstract at the 58th AAVLD/119th USAHA Annual Meeting, October
22–28, 2015.7
In this case, the superior sensitivity of the SNAP test is likely due
to the bidirectional flow and signal amplification features of ELISA
technology. These enhanced components of the SNAP assay are
not present in the VetScan and Witness lateral flow tests.8 Optimal
test sensitivity allows for early supportive care and helps to prevent
transmission of the virus to naïve cats.

References1.	Hartmann K. Feline leukemia virus infection. In: Greene CE, ed. Infectious
Diseases of the Dog and Cat. 4th ed. St Louis, MO: Saunders; 2012:108–136.
2.	Levy J, Crawford C, Hartmann K, et al. American Association of Feline
Practitioners’ feline retrovirus management guidelines. J Feline Med Surg.
2008;10(3):300–316.
3.	Lutz H, Pedersen NC, Theilen GH. Course of feline leukemia virus infection
and its detection by enzyme-linked immunosorbent assay and monoclonal
antibodies. Am J Vet Res. 1983;44(11):2054–2059.
4.	Hartmann K, Griessmayr P, Schulz B, et al. Quality of different in-clinic tests
systems for feline immunodeficiency virus and feline leukemia virus infection.
J Feline Med Surg. 2007;9(6):439–445.
5.	Hartmann K, Werner RM, Egberink H, Jarrett O. Comparison of six in-house tests
for the rapid diagnosis of feline immunodeficiency and feline leukaemia virus
infections. Vet Rec. 2001;149(11):317–320.
6.	Goldkamp CE, Levy JK, Edinboro CH, Lachtara JL. Seroprevalences of feline
leukemia virus and feline immunodeficiency virus in cats with abscesses or bitewounds and rate of veterinarian compliance with current guidelines for retrovirus
testing. JAVMA. 2008;232(8):1152–1158.
7.	Lappin M, Thatcher B, Liu J, Bewsey H, Beall M, O’Connor T, Chandrashekar
R. Evaluation of three in-clinic serological tests for specific detection of FeLV
antigen in cats. Paper presented at: 58th AAVLD/119th USAHA Annual Meeting;
October 22–28, 2015; Providence, RI.
8.	O’Connor TP, Lawrence J, Andersen P, Leathers V, Workman E. Immunoassay
Applications in Veterinary Diagnostics. In: Wild D, ed. The Immunoassay
Handbook: Theory and Applications of Ligand Binding, ELISA and Related
Techniques. Oxford, England: Elsevier; 2013:623–645.

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