# Neutrophil-to-Lymphocyte Ratio as a Promising Non-Invasive Biomarker for Diagnosis of Feline Idiopathic Cystitis in Cats

## TL;DR

This study shows that the neutrophil-to-lymphocyte ratio (NLR) can help diagnose feline idiopathic cystitis in cats with high accuracy.

## Contribution

The study identifies NLR as a potential non-invasive biomarker for diagnosing feline idiopathic cystitis.

## Key findings

- NLR levels in FIC cats were significantly higher than in healthy cats (p < 0.001).
- NLR showed a strong negative correlation with FIC (r = −0.8439, p < 0.0001).
- NLR had high diagnostic accuracy with an AUC of 0.9872 in distinguishing FIC from healthy cats.

## Abstract

Feline idiopathic cystitis (FIC) is a chronic disorder of the lower urinary tract in cats. At present, the disease is mainly excluded by evaluating the results of blood, urine, and imaging examinations of diseased animals. There is still a lack of clear and objective indicators for the diagnosis of FIC in clinical practice. In this study, the correlation between NLR and FIC was analyzed by collecting the complete blood count data of FIC cats and healthy cats. The results of the inter-group difference comparison showed that the NLR levels in the normal group were distinctly lower than that in the FIC group (p < 0.001). Spearman correlation analysis showed that there was a significant correlation between NLR and FIC (r = −0.8439, p < 0.0001). ROC analysis showed that NLR had high diagnostic accuracy in distinguishing healthy cats from FIC cats (AUC = 0.9872). Therefore, the NLR parameter holds the potential to serve as a non-invasive biomarker of FIC.

Feline idiopathic cystitis (FIC) is a common chronic cystitis disease in cats, accounting for 55–65% of feline lower urinary tract disease (FLUTD). The common clinical symptoms of FIC include pollakiuria, periuria, hematuria, and dysuria. At present, the disease is mainly excluded by evaluating the results of blood, urine, and imaging examinations of diseased animals. There is still a lack of clear and objective indicators for the diagnosis of FIC in clinical practice. Neutrophil-to-lymphocyte ratio (NLR) can be used as an indicator to measure immune inflammatory response and neuroendocrine pressure. It is an economical, efficient, and simple calculation method. In this study, the correlation between NLR and FIC was analyzed by collecting the complete blood count data of FIC cats and healthy cats. The results of inter-group difference comparison showed that the LYMPH levels in the normal group were significantly higher than that in the FIC group (p < 0.001), and the NEUT levels and NLR levels were distinctly lower than those in the FIC group (p < 0.001). Spearman correlation analysis showed that there was a significant correlation between NLR and FIC (r = −0.8439, p < 0.0001). ROC analysis showed that NLR had high diagnostic accuracy in distinguishing healthy cats from FIC cats (AUC = 0.9872). In general, this study preliminarily confirmed that there was a significant correlation between NLR elevation and FIC, emphasizing the prospective utility of NLR as a promising biomarker for diagnosis in FIC. Because of the lack of uniform diagnostic criteria for FIC, NLR may provide important help in the diagnosis process.