However, in a clinical trial, the sensitivities of the urinary TAP-to-creatinine ratio and plasma TAP concentration for pancreatitis
in dogs were suboptimal.26 The urinary TAP-to-creatinine ratio was highly specific for pancreatitis (specificity 100%) but was not sensitive, identifying
only 26% of all dogs with pancreatitis.26
A recent study also evaluated serum and urinary TAP concentrations for diagnosing feline pancreatitis.29 While the urinary TAP concentration and urinary TAP-to-creatinine ratio were not significantly different in cats with pancreatitis
compared with clinically healthy cats, the serum TAP concentration was significantly increased in cats with pancreatitis.29 However, the serum TAP concentration did not appear to have any advantages over the determination of serum TLI concentration.29 Also, TAP is relatively labile in plasma and urine samples, and the assay is not widely available. Thus, the use of this
assay for diagnosing pancreatitis in dogs and cats cannot be recommended.
Pancreatic lipase immunoreactivity
Recently, pancreatic lipase immunoreactivity (PLI) assays have been developed and validated for dogs and cats (cPLI and fPLI,
respectively).30,31 As mentioned previously, many different cell types in the body synthesize and secrete lipases. In contrast to catalytic
assays for measuring lipase activity, immunoassays allow the specific measurement of lipase originating from the exocrine
Serum cPLI concentration was measured in 25 dogs with exocrine pancreatic insufficiency, and the median serum cPLI concentration
was significantly decreased compared with clinically healthy dogs.19 In addition, the serum cPLI concentration was undetectable in most (80%) of the dogs, indicating that the serum cPLI concentration
mostly, if not exclusively, originates from the exocrine pancreas.19
In another study, serum cPLI concentrations were evaluated in 16 dogs with experimentally induced chronic renal failure.32 While serum cPLI concentrations were significantly higher in dogs with experimentally induced chronic renal failure than
in clinically healthy dogs, 14 dogs had serum cPLI concentrations within the reference range, and none of the dogs had serum
cPLI concentrations that were above the currently recommended cut-off value for pancreatitis.32
These data suggest that the serum cPLI concentration can be used as a diagnostic test for pancreatitis even in dogs with renal
failure.32 Also, long-term oral administration of prednisone (2.2 mg/kg once a day for four weeks) in six healthy dogs did not affect
the serum cPLI concentration.33 Finally, the sensitivity of different minimally invasive diagnostic tests was compared in 11 dogs with pancreatitis.27 The sensitivity of the serum TLI concentration was below 35% and that of serum lipase activity was less than 55%. In contrast,
the sensitivity of the serum cPLI concentration for pancreatitis was above 80%.27
Recent studies in cats have shown similar results. In six cats with experimentally induced pancreatitis, both serum fTLI and
fPLI concentrations did increase initially, but the serum fPLI concentration stayed elevated much longer than did the serum
fTLI concentration, suggesting that, as in dogs, the serum PLI concentration is more sensitive for pancreatitis than is the
serum TLI concentration.34 In another study in cats with spontaneous pancreatitis, the serum fPLI concentration was more sensitive and more specific
than was the serum fTLI concentration or abdominal ultrasonography.8
While the serum PLI concentration does not allow differentiation of acute vs. chronic pancreatitis, it can be used to monitor
the progress of disease (see the article "Serial serum pancreatic lipase immunoreactivity concentrations in a dog with histologically confirmed pancreatitis"
in this issue).
These initial data suggest that the serum PLI concentration is highly sensitive and specific for diagnosing pancreatitis in
dogs and cats. Further studies and long-term clinical experience with these new tests are required to confirm these findings.
A commercial assay for measuring cPLI concentration (Spec cPL—Idexx Laboratories) has recently been released and is expected
to increase the availability of cPLI measurement for veterinary practitioners. In contrast, the fPLI assay is only available
through the Gastrointestinal Laboratory at Texas A&M University's Department of Small Animal Clinical Sciences (