Seven FIV and 8 FeLV tests were compared for the following: diagnostic sensitivity and specificity, percentage of invalid test results, percentage of results that were difficult to interpret, and positive and negative predictive values. Serum samples from 536 randomly selected cats were tested. Samples testing FIV-positive in 1 or more tests (55 of 536 samples) were confirmed by Western blot analysis, and those testing FeLV-positive in 1 or more tests (39 of 528 samples) were confirmed by virus isolation. Of the FIV test systems, 1 (Mapic FIV, was found to be unacceptable due to the high percentage of invalid test results and results that were difficult to interpret. The remaining FIV test systems were found to be good overall, with similarly high sensitivity and specificity as well as predictive values. The Snap Combo Plus ( test had the best overall results. The Mapic FeLV system was also found to be unacceptable due to the high number of invalid test results and the percentage of tests that were difficult to interpret. A second test (One-Step, was not considered acceptable as a single test but could be used in combination with other tests to increase positive predictive value. Of the remaining FeLV tests, Duo Speed ( had the best overall performance and thus was considered the best in-house test for FeLV. Combined tests were also evaluated to see whether combinations would yield higher positive predictive values. For FIV testing, Snap Combo Plus was recommended as the best in-clinic test, with the second best being Fastest ( or Duo Speed. For FeLV testing, Duo Speed was recommended as the best in-clinic test with second-testing of a positive sample using Witness ( or Fastest. Study funded in large part by Idexx

COMMENTARY: Testing to identify FeLV- and FIV-infected cats is the mainstay of preventing transmission of these viruses. Thus, reliable test systems are critical. A number of different types of diagnostic tests are available, with immunoassays being the most widely used in practice. Information on the performance of these tests, however, can conflict, and there are shortcomings to any method used as a confirmatory test. This article is useful in helping to decide which tests might be best suited for initial screening. The AAFP has previously recommended that positive results be confirmed by other forms of testing-particularly if a cat has no clinical signs or when a low-prevalence population is being tested-and this study reinforces this message.

Quality of different in-clinic test systems for feline immunodeficiency virus and feline leukaemia virus infection. Hartmann K, Griessmayr P, Schulz B, et al. J FELINE MED SURG 9:439-445, 2007.