The evaluation was based on partial verification
which is a valid and efficient option when
disease events are not prevalent in a population,
and verification of all samples would be too
costly and time-consuming (Greiner 1999). The
test considered as gold standard (Western blot
for FIV positivity and virus isolation for FeLV
positivity) was performed on each sample that
had yielded a positive result in at least one test
system and, in addition, on 100 (Western blot)
and 81 (FeLV virus isolation) negative samples,
respectively. Calculation of the confidence intervals
was performed using ‘confidence interval
analysis’ (Altmann et al 2000) based on the
method of Wilson (1927).