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Abstract Background Differentiation of gastrointestinal cancer (GIC) from chronic inflammatory enteropathies (CIE) in cats can be challenging and often requires extensive diagnostic testing. MicroRNAs (miRNAs) have promise as non‐invasive biomarkers in serum and feces for diagnosis of GIC. Hypothesis/Objectives Cats with GIC will have serum and fecal miRNA profiles that differ significantly from healthy cats and cats with CIE. Identify serum and fecal miRNAs with diagnostic potential for differentiation between cats with GIC and CIE as compared to healthy cats. Animals Ten healthy cats, 9 cats with CIE, and 10 cats with GIC; all client‐owned. Methods Cats were recruited for an international multicenter observational prospective case‐control study. Serum and feces were screened using small RNA sequencing for miRNAs that differed in abundance between cats with GIC and CIE, and healthy cats. Diagnostic biomarker potential of relevant miRNAs from small RNA sequencing and the literature was confirmed using reverse transcription quantitative real‐time PCR (RT‐qPCR). Results Serum miR‐223‐3p was found to distinguish between cats with GIC and CIE with an area under the curve (AUC) of 0.9 (95% confidence interval [CI], 0.760‐1.0), sensitivity of 90% (95% CI, 59.6‐99.5%), and specificity of 77.8% (95% CI, 45.3‐96.1%). Serum miR‐223‐3p likewise showed promise in differentiating a subgroup of cats with small cell lymphoma (SCL) from those with CIE. No fecal miRNAs could distinguish between cats with GIC and CIE. Conclusion and Clinical Importance Serum miR‐223‐3p potentially may serve as a noninvasive diagnostic biomarker of GIC in cats, in addition to providing a much needed tool for the differentiation of CIE and SCL.

Abstract Background Reliable biomarkers to differentiate gastrointestinal cancer (GIC) from chronic inflammatory enteropathy (CIE) in dogs are needed. Fecal and serum microRNAs (miRNAs) have been proposed as diagnostic and prognostic markers of GI disease in humans and dogs. Hypothesis/Objectives Dogs with GIC have fecal and serum miRNA profiles that differ from those of dogs with CIE. Aims: (a) identify miRNAs that differentiate GIC from CIE, (b) use high‐throughput reverse transcription quantitative real‐time PCR (RT‐qPCR) to establish fecal and serum miRNA panels to distinguish GIC from CIE in dogs. Animals Twenty‐four dogs with GIC, 10 dogs with CIE, and 10 healthy dogs, all client‐owned. Methods An international multicenter observational prospective case‐control study. Small RNA sequencing was used to identify fecal and serum miRNAs, and RT‐qPCR was used to establish fecal and serum miRNA panels with the potential to distinguish GIC from CIE. Results The best diagnostic performance for distinguishing GIC from CIE was fecal miR‐451 (AUC: 0.955, sensitivity: 86.4%, specificity: 100%), miR‐223 (AUC: 0.918, sensitivity: 90.9%, specificity: 80%), and miR‐27a (AUC: 0.868, sensitivity: 81.8%, specificity: 90%) and serum miR‐20b (AUC: 0.905, sensitivity: 90.5%, specificity: 90%), miR‐148a‐3p (AUC: 0.924, sensitivity: 85.7%, specificity: 90%), and miR‐652 (AUC: 0.943, sensitivity: 90.5%, specificity: 90%). Slightly improved diagnostic performance was achieved when combining fecal miR‐451 and miR‐223 (AUC: 0.973, sensitivity: 95.5%, specificity: 90%). Conclusions and Clinical Importance When used as part of a diagnostic RT‐qPCR panel, the abovementioned miRNAs have the potential to function as noninvasive biomarkers for the differentiation of GIC and CIE in dogs.