The Clinical Significance of the Derived Neutrophil-to-Lymphocyte Ratio in Differentiating Occult Psoriatic Arthritis from Psoriasis Alone

Background. Occult psoriatic arthritis (PsA) refers to a subset of psoriasis patients showing lesions on imaging but do not exhibit arthritis symptoms. Objective. This study was aimed to discover a simple biomarker that could be easily incorporated in clinical practice to identify occult PsA patients, defined as psoriasis patients with lesions on imaging but without arthritis symptoms, among silent psoriasis (PsO) patients, defined as psoriasis patients without any arthritis symptoms. Methods. A total of 149 silent PsO patients, including 83 PsO alone patients, defined as psoriasis patients without any arthritis symptoms and evidence of lesions on imaging, and 66 occult PsA patients, were enrolled in this cross-sectional study, and they all underwent blood tests to determine hematological inflammation biomarkers. Results. Occult PsA patients had a higher derived neutrophil-to-lymphocyte ratio (dNLR) (1.6 (1.3–2.2) vs. 1.3 (0.9–1.8), $p$ < 0.001), body mass index (BMI) (25.2 (23.7–28.1) vs. 24.0 (21.9–26.0), $p$ = 0.002), diabetes mellitus (DM) rate (30.3% vs. 7.2%, $p$ < 0.001), and nail involvement rate (65.2% vs. 41.0%, $p$ = 0.003) than patients with PsO alone. A prediction nomogram was established, and the area under the curve (AUC) was 0.843. The sensitivity and specificity of the model for identifying occult PsA patients were 77.3% and 81.9%, respectively. Conclusion. Our findings suggest that dNLR is a valuable diagnostic biomarker for occult PsA, and our prediction nomogram could provide clinicians with a useful tool for differentiating occult PsA patients from PsO alone patients.