GASTRO-ENTEROLOGY
oratory assessment of A1-PI as a diagnostic test for
intestinal protein loss is performed infrequently. This
laboratory assay may be most useful in assessing response to therapy in dogs with PLEs.
Serum albumin
Hypoalbuminemia has been associated with a negative outcome in separate canine IBD studies. Severe
IBD and other chronic enteropathies may predispose
patients to hypoalbuminaemia due to enteric plasma
protein loss as well as nutritional deficiencies and nutrient malabsorption.
One retrospective study found a low serum albumin
concentration was associated with a negative outcome (i.e. poor clinical response to dietary and drug
therapies or euthanasia) in 80 dogs diagnosed with
IBD. In my experience, dogs having severe hypoalbuminemia (< 1.5 g/l) with cavity effusion, salient GI
signs, or both are at greater risk for negative outcome
(euthanasia).
Intestinal inflammation and damage markers
Several serologic markers for inflammation have been
designed to predict the disease course and response
to therapy of canine chronic enteropathies.
pANCA
Titers for perinuclear antineutrophil cytoplasmic antibodies (pANCA) have been evaluated as diagnostic
markers in canine IBD in separate studies. In one study
of 31 dogs, results indicated that pANCA was a highly
specific marker for IBD, although the sensitivity of the
assay was too low to be of value as a screening test.
This immunofluorescence assay was shown to be
most useful in detecting dogs with food-responsive
enteropathy at the time of diagnosis.
More recently, pANCA was shown to be a highly specific serologic marker vs. antinuclear antibody testing
for differentiating IBD from other GI disorders. In addition, other studies have shown that pANCA is of value
as a diagnostic marker for familial PLE in soft-coated
Wheaten Terriers. Unfortunately, this assay is not readily available and is presently limited for use in research
investigations.
CRP
C-reactive protein (CRP) is an acute phase protein produced by the liver in response to inflammation. It is a
sensitive but nonspecific inflammatory marker shown
to correlate with moderate to severe clinical disease
activity in canine IBD. This marker is the best-characterised inflammatory marker as no fewer than four
different studies have shown that dogs with IBD have
heterogeneous serum elevations of this marker.
New studies have evaluated the index of variability for
CRP, suggesting that the use of a population-based
reference range is not appropriate for evaluating
References available on www.vet360.vetlink.co.za
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Issue 06 | DECEMBER 2016 | 16
changes in CRP in individual patients. Instead, serial
CRP measurements should be performed and modest changes in serum CRP may indicate the initial severity of GI disease and its alteration from baseline in
response to therapeutic intervention.
Fecal calprotectin and other S100A proteins
Calprotectin and S100 A8/A9 and A12 are calcium-binding proteins found predominantly within neutrophils and other immune cells in inflamed mucosa. Fecal concentrations of these proteins have been
recently shown to be increased in people and dogs
with IBD when compared with healthy controls. Importantly, the S100 A12 fecal marker has greater sensitivity for the detection of intestinal inflammation and
has been positively associated with endoscopy and
clinical scores.
P-GP
The expression of P-glycoprotein (P-GP) in mucosal lymphocytes has also been investigated and
shown to be up-regulated in dogs with IBD treated
with prednisolone. This earlier study showed that in
dogs with steroid-responsive enteropathy, low P-GP
expression was associated with a good therapeutic
response.
Practical molecular tools
PARR
Polymerase chain reaction for antigen receptor rearrangements (PARR) amplifies variable T or B cell antigen genes and is used to detect a clonally expanded
population of lymphocytes. This molecular technique
is useful in differentiating severe mucosal inflammation (severe IBD) from alimentary lymphoma. PARR
is often performed when histologic examination and
immunophenotyping return ambiguous results. Data
derived from feline studies show that this molecular
technique is highly sensitive for differentiating between intestinal lymphoma and IBD. However, further
studies are needed to assess this technique’s value
and sensitivity in dogs.
FISH
Fluorescence in situ hybridization (FISH) is a molecular technique used to identify microbial populations
in tissues. FISH analysis has been applied to a variety of GI tissues, including the pancreas, liver, and alimentary tract, in dogs and cats. This technique uses
culture-independent analysis of bacterial 16S or 23S
rDNA genes targeted by DNA probes tagged with a
fluorophore. Bacterial populations are then imaged
via fluorescence microscopy. Microbial imbalances in
diseased GI tissues (e.g. Helicobacter species gastritis, idiopathic IBD, feline cholangitis) in dogs and cats
have been demonstrated using FISH techniques. Specifically, FISH has identified an association between GI
inflammation and a shift in the microbiome by means
of bacterial translocation or dysbiosis of mucosa-associated microbial popu lations.