Background: The neutrophil-to-lymphocyte ratio (NLR) has been identified as a biomarker in several inflammatory and autoimmune diseases. Multiple sclerosis (MS) has been found to be associated with changes in the NLR in humans. Objectives: To examine the diagnostic value of the NLR in meningoencephalitis of unknown etiology (MUE) in dogs. Animals: Thirty-eight MUE dogs, 20 hydrocephalic dogs, 10 brain tumor (BT) dogs, 32 idiopathic epilepsy (IE) dogs, and 41 healthy dogs. Methods: Retrospective study. Medical records were reviewed to identify dogs with a diagnosis of neurologic disease. The NLR was determined in all dogs. Results: The median NLR was significantly higher in MUE dogs (6.08) than in healthy (1.78, P < .001), IE (2.50, P < .05), and hydrocephalic dogs (1.79, P < .05). The area under the receiver operating characteristic curve of the NLR for differentiation between MUE and healthy dogs was 0.96, and between the MUE dogs and dogs with other forebrain diseases was 0.86. An optimal cutoff of 4.16 for the NLR had a sensitivity of 71.1% and specificity of 83.9% to differentiate the MUE dogs from the dogs with other forebrain diseases. Conclusions and Clinical Importance: The NLR could be a biomarker for diagnosing MUE and distinguishing it from other intracranial diseases in dogs.

Background Neurofilament light chain (NfL) is a neuron-specific cytoskeletal protein expressed in axons. Damaged axons of the central nervous system release NfLs into the cerebrospinal fluid (CSF) and the blood. In humans with neurologic diseases, NfL is used as a biomarker. Objectives To identify the potential of NfL as a supportive tool for the diagnosis, prognosis, and monitoring of meningoencephalitis of unknown etiology (MUE) in dogs. Animals Twenty-six client-owned healthy dogs, 10 normal Beagle dogs, and 38 client-owned MUE dogs. Methods Cohort study. The concentrations of NfL in serum and CSF were measured using single-molecule array technology. Results Median NfL concentration was significantly higher in MUE dogs (serum, 125 pg/mL; CSF, 14 700 pg/mL) than in healthy dogs (serum, 11.8 pg/mL, P < .0001; CSF, 1410 pg/mL, P = .0002). The areas under the receiver operating characteristic curves of serum and CSF NfL concentrations were 0.99 and 0.95, respectively. The cut-off values were 41.5 pg/mL (serum) and 4005 pg/mL (CSF) for differentiating between healthy and MUE dogs, with sensitivities of 89.19% and 90%, respectively, and specificities of 96.97% and 100%, respectively. The NfL concentration showed a significant decrease (pretreatment, 122 pg/mL; posttreatment, 36.6 pg/mL; P = .02) in the good treatment-response group and a significant increase (pretreatment, 292.5 pg/mL; posttreatment, 1880 pg/mL, P = .03) in the poor treatment-response group. Conclusions and Clinical importance Neurofilament light chain is a potential biomarker for diagnosing MUE and evaluating response to treatment.

Background Inflammatory bowel disease (IBD) commonly occurs in dogs, but there is lack of information about potential biomarkers of clinical and histopathologic severity. Objective To examine the role of serum C-reactive protein (CRP) and high-mobility group box 1 (HMGB1) concentrations in dogs with IBD. Animals Seventeen dogs with IBD and 25 healthy dogs. Methods In this prospective study, duodenal histopathologic severity was graded, and the clinical severity of IBD was assessed by the canine IBD assessment index (CIBDAI) score in dogs with IBD. Serum CRP and HMGB1 concentrations were compared between IBD and healthy dogs and analyzed according to histopathologic grade in dogs with IBD. The correlations between serum CRP and HMGB1 concentrations and the CIBDAI score were evaluated. Results Dogs with IBD had higher serum CRP (median [range] = 20.39 [1.53-67.69] μg/mL vs 2.31 [0.17-11.49] μg/mL; P < .001) and HMGB1 concentrations (0.44 [0.07-1.58] ng/mL vs 0.05 [0.01-0.25] ng/mL; P < .001) than healthy dogs. The serum HMGB1 concentration was higher in IBD dogs with a moderate to severe histopathologic grade (0.51 [0.30-1.58] ng/mL, P = .03) than in those with a mild histopathologic grade (0.17 [0.07-0.75] ng/mL). Serum CRP concentrations and CIBDAI score were positively correlated in dogs with IBD (r_s = .49, P = .05). Conclusions and Clinical Importance Serum HMGB1 could be a potential biomarker for diagnosing IBD and might be indicative of histopathologic severity in dogs, whereas serum CRP might be an indicator of clinical severity.

Sora Lee, Taesik Yun, Yoonhoi Koo, Yeon Chae, Dohee Lee, Dongjoon Choi, Yujin Choi, Hakhyun Kim, Mhan-Pyo Yang, Byeong-Teck Kang. J Vet Clin 2021;38:127-34. https://doi.org/10.17555/jvc.2021.38.3.127

Background: Neurofilament light chain (NfL) is an axonal cytoplasmic protein in neurons. Recently, NfL has shown potential as a diagnostic biomarker in dogs with meningoencephalitis of unknown origin (MUO). However, there have been no studies on the biomarkers of lesion progression and resolution in MUO.Objectives: To identify the potential of NfL as a biomarker for predicting changes in lesions.Methods: Seven dogs with MUO who had undergone two magnetic resonance imaging (MRI) scans were included. The serum NfL levels were measured using a single‐molecule array. The relationship between the rate of change in lesion size and the rate of change in serum NfL level was analysed using simple linear regression. To investigate the effect of changes in lesion size on NfL levels, the dogs were divided into two groups depending on the change in lesion size: decreased lesion size group (n = 5) and increased lesion size group (n = 2). Trends in lesion size change were identified in the second MRI compared with the first MRI.Results: A significant positive relationship between the rate of lesion size change and the rate of NfL level change was identified (R² = 0.9239, p = 0.0006). In the decreased lesion size group (n = 5), all NfL levels in each dog decreased, and in the increased lesion size group (n = 2), all NfL levels in each dog increased.Conclusions: This preliminary study showed a positive relationship between the rate of change in lesion size and rate of change in serum NfL levels. Therefore, the serum NfL level may be a promising biomarker of lesion progression and resolution in MUO.

Background: Neurofilament light chain (NfL) is released into the peripheral circulation by damaged axons. Objectives: To evaluate the diagnostic value of serum NfL concentration in dogs with intracranial diseases. Animals: Study included 37 healthy dogs, 31 dogs with idiopathic epilepsy (IE), 45 dogs with meningoencephalitis of unknown etiology (MUE), 20 dogs with hydrocephalus, and 19 dogs with brain tumors. Methods: Cohort study. Serum NfL concentrations were measured in all dogs using single-molecule array technology. Results: Serum NfL concentration in dogs with each structural disease was significantly higher than in healthy dogs and dogs with IE (P = .01). The area under the receiver operating characteristic curve of NfL for differentiating between dogs with structural diseases and IE was 0.868. An optimal cutoff value of the NfL 27.10 pg/mL had a sensitivity of 86.67% and a specificity of 74.19% to differentiate the dogs with IE from those with structural brain diseases. There were significant correlations between NfL concentrations and lesion size: (1) MUE, P = .01, r = 0.429; (2) hydrocephalus, P = .01, r = 0.563. Conclusions and Clinical Importance: Serum NfL could be a useful biomarker for distinguishing IE from structural diseases in dogs and predicting the lesion sizes of MUE and hydrocephalus.