CLINICAL PATHOLOGY
Sensitivity of a test means “positivity in disease”, which means a sensitive test has no or few false negatives. The more
sensitive a test the more likely you are to get false positives if your test population is not properly selected.
Specificity means” negativity in health” - which means few or no false positive test results. The more specific a test is
the more likely you are to get a false positive in a poorly selected test population.
With the Spec cPL test: We know that histopathological pancreatic inflammation is present in many animals, which
have mild or no signs of disease. So if we use histopathological changes as the gold standard for pancreatitis the
test may be very specific (very few false positives) but if we were to use “clinically confirmed” pancreatitis using best
available clinical, biochemistry and abdominal ultrasound evidence as our gold standard the specificity will be lower,
more positives in the absence of clinical disease. This makes sense as we know some animals walk around with mild
inflammation and no clinical signs. These numbers are not written in stone as they vary depending on what they are
measured against.
SNAP cPL should be performed in any dog with acute
signs of gastrointestinal disease which does not have
an obvious diagnosis such as intestinal parasites, foreign body, Parvo-virus infection, etc. The SNAP test
only gives either a negative or positive result and is
slightly more sensitive but less specific than the Spec
cPL. If the test is negative then pancreatitis can essentially be ruled out as the sensitivity of the SNAP
is 93% which gives a 7% chance of a false negative.4
A positive SNAP cPL indicates a lipase value of ≥
200ug/L. However, as a positive Snap cPL, is NOT
a 100% diagnostic positive diagnosis for pancreatitis,
it is still the responsibility of the clinician to perform
a full diagnostic workup. Ideally an abdominal ultrasound should be performed to exclude other abdominal conditions which could cause similar clinical signs
and also cause lipase release.
In addition, measurement of Spec cPL should be done
to help confirm diagnosis of pancreatitis. The Spec
cPL is a quantitative test with 3 diagnostic ranges: normal reference range (< 200 ug/L), questionable range
(between 200-400 ug/L), and diagnostic cut-off for
pancreatitis (≥ 400 ug/L) (IDEXX package insert). The
magnitude of elevation of serum canine pancreatic
lipase concentration does, however, not establish a
prognosis for a patient with acute pancreatitis nor is
there evidence that changes in serum concentrations
correspond to clinical improvement.1
The sensitivity of Spec cPL in various studies ranges
from 21% in dogs with histopathologically confirmed
mild pancreatitis; 71% in dogs with severe pancreatitis;
and up to 87% in some cases.4 It would appear that
the greater the pancreatic inflammation the greater
the test sensitivity, which would make sense as more
lipase is release into the bloodstream and these dogs
have more severe clinical signs thus the prevalence
in the test population is higher. Thus there is about a
15-25% possibility of having a false negative diagnosis.
The Spec cPL sensitivity has also been measured
against an increase between > 200- 399 ug/L (90%)
and an increase > 400ug/L( 75%) thus it decreases as
the cutoff increases - but the specificity will increase
with an increased cutoff. The specificity is 74% for the
SNAP, 72% for Spec cPL cutoff between 200 -399ug/L
and 78% with a cutoff > 400ug/L.4
Spec cPL cannot differentiate between primary and
secondary pancreatitis — some dogs with an inflammatory disease process in another organ in the region
of the pancreas (liver, gall bladder, mesentery, peritoneum) may have secondary pancreatic inflammation
and animals with primary intestinal disease (foreign
body, inflammatory bowel disease, lymphoma) may
show elevated lipase values.1,2
Two recent studies investigating risk factors for pancreatitis showed that many dogs had co-existing disease and that there appeared to be an association
between the presence of Cushing’s disease and the
development of pancreatitis. Dogs with Cushing’s
disease and no clinically diagnosed pancreatitis had
a higher Spec cPL concentrations and more positive
SNAP cPL results than clinically healthy dogs with
normal ACTH stimulation test results. Spec cPL test
concentrations were significantly higher in dogs with
Cushing’s disease (491.1 ug/L) than in healthy dogs
(75.2 ug/L), with more abnormal Spec cPL results
in Cushing’s dogs. There were more positive SNAP
results in dogs with Cushing’s disease (55%) than in
healthy dogs (6%).3
In another study, SNAP cPL and Spec cPL was evaluated in 3 groups of dogs: healthy dogs (n=20), those
with signs of Cushing’s disease but normal ACTH
stimulation test results (n=12), and dogs with confirmed Cushing’s disease (n=20). Dogs were excluded
from the study if they had any clinical signs suggestive
of pancreatitis. Healthy dogs had one SNAP cPL positive test and one Spec cPL in the 200-400g/L range.
In the second group, 3/12 dogs had a positive SNAP
cPL and 2 dogs had Spec cPL consistent with pancreatitis. In dogs with confirmed Cushing’s disease,
11/20 had a positive SNAP cPL and 5 had a Spec cPL
Th
e
and the spec cPL can give both false positives and
negative results.1
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vet360
Issue 02 | APRIL 2016 | 38
April 2016 Vet360 for Madaleen Review.indd 38
2016/03/24