A study mentioned by IDEXX on their product
information sheet shows the sensitivity and specificity of the SNAP and Spec
cPL tests to be 93% and 78% (McCord K. et. al, 2012) respectively, however
since this relates to one of their own products we compared this to other
A separate publication quoted the sensitivity and
specificity of the SNAP cPL test to be 82% and 59% respectively. This is a
closer comparison to the values we calculated; 83.33% for sensitivity and
51.72% for specificity. Both the values we calculated and those published were
lower than the values reported by IDEXX, in particular the specificity is ~20%
lower than quoted. Compared to the SNAP test, the Spec cPL test was reported as
having a sensitivity and specificity of 70% and 77% respectively. This compares
well with our calculated values for Spec cPL sensitivity and specificity which
were; 72.22% and 79.31% respectively. The accuracy also quoted in this study
was 66% for the SNAP cPL and 75% for the Spec cPL test (Haworth MD, et. al,
2014). This compared to our calculated results (SNAP: 63.83% and Spec: 76.60%)
closely, with only slight differences between the values.
Two studies, the first of which was carried out
on 84 dogs, reported their findings of sensitivity of the Spec cPL diagnostic
test to be between 86-94% (on a cut off value of 200?g/L) (Xenoulis, P. G. et. al, 2016).
This is quite a difference in comparison to our calculated value for the
sensitivity of Spec cPL (72.22%). They also reported the sensitivity of the
SNAP cPL test as ranging between 91-94%, which is also much higher than we
expected (83.33%). The second study, only contained 38 dogs, however the
results compared more closely with the our calculated values, previously
mentioned. Spec sensitivity was published as 70% and SNAP sensitivity as 82% (Xenoulis, P. G. et. al, 2016),
compared to 72.22% and 83.33% respectively.
Overall, I think some publications are more
reliable than others. The information released by IDEXX may be less accurate
than reviewed data since they can use data to sell their product (SNAP cPL
Test). Tests including more patients would also be assumed to be more accurate,
however there are examples of studies which quote similar values to IDEXX
themselves which makes it difficult to know which studies can be trusted.
However, since all studies came up with values within roughly the same ranges,
it can be said that the methods they are using to analyse such diagnostic tests
must be somewhat accurate.