Neutrophil-to-Lymphocyte Ratio in Canine Inflammatory Bowel Disease

In the literature

Benvenuti E, Pierini A, Gori E, Lucarelli C, Lubas G, Marchetti V. Neutrophil-to-lymphocyte ratio (NLR) in canine inflammatory bowel disease (IBD). Vet Sci. 2020;7(3):141.

The Research …

Canine inflammatory bowel disease (IBD) is characterized by idiopathic intestinal inflammation and lack of response to diet and antibiotic treatments.¹ Histopathology of the intestinal tract and response to immunosuppressive therapy are required for definitive diagnosis. Factors associated with negative outcomes for dogs with IBD include the chronic canine enteropathy clinical activity index (CCECAI), a high endoscopic score in the duodenum, hypocobalaminemia (<200 ng/L), and hypoalbuminemia (<20 g/L).²

Predictive markers are still needed to classify IBD-affected dogs into risk groups. One such prospective marker is the neutrophil:lymphocyte ratio (NLR). During inflammatory states, the neutrophil count may increase whereas the lymphocyte count may decrease.³ NLR is an accessible parameter that can easily be calculated as a ratio between absolute neutrophils and lymphocytes using a WBC count differential.³ In studies of human patients with IBD, NLR appeared to be higher in patients with active disease.⁴

This retrospective study evaluated the clinical and prognostic significance of NLR in dogs with IBD. NLR of healthy control dogs (n = 150) was compared with dogs with IBD (n = 41). The correlation between NLR and several variables, including CCECAI and endoscopic histology scores, was investigated. After one month of treatment with immunosuppressive therapy, differences in NLR between responders and nonresponders were assessed.

Results revealed that dogs with IBD had higher median NLRs than the control dogs (4.78 vs 3), although most dogs with IBD had neutrophil and lymphocyte counts within reference intervals. There was a moderate positive correlation between NLR and CCECAI at the time of admission, which supports the potential use of NLR as a marker of clinical disease severity in canine IBD. NLR seemed to be negatively correlated with total protein, albumin, and cholesterol levels. NLR was higher in dogs diagnosed with protein-losing enteropathy, potentially due to loss of lymphocytes through ruptured lacteals.⁴ The only significant histologic parameter associated with NLR was the presence of lacteal dilation. In the study population, NLR did not differ significantly between endoscopic or histologic score groups. After one month of immunosuppressive therapy, the median NLR was significantly higher in nonresponders than responders (12.23 vs 4.58).

… The Takeaways

Key pearls to put into practice:

• Because of its poor sensitivity and specificity, increased NLR should not be used as the sole diagnostic criteria for canine IBD or lymphangiectasia. Although it can be used to further support suspicion of these disorders, histologic diagnosis is still required.

• NLR has potential use as a marker of disease severity in canine IBD as well as for clinical monitoring of therapeutic response in cases of chronic enteropathies. NLR can be easily calculated by dividing the absolute neutrophil count by the absolute lymphocyte count using the results of routine blood work.

• NLR can be impacted by stress and chronic disease states. The extent of impact has not been examined, and further studies are needed.