Vet360, December 2016 - Page 16

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 vet360 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.