Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio in Adult-Onset Still Disease, their Relationship with Baseline Disease Activity and Subsequent Disease Course: A Single-Center Retrospective Cohort Study

Abstract

Introduction: Adult-onset Still Disease (AoSD) is a rare systemic polygenic nonfamilial autoinflammatory disease of unknown aetiology. The long-term course of the disease can be categorised in three different definitions including self-limited course, intermittent course or chronic course. Recently, Neutrophil-to-Lymphocyte Ratio (NLR) and Platelet-to-Lymphocyte Ratio (PLR) were investigated in various rheumatic diseases as an informative markers in evaluating severity of inflammation and disease activity. Aim: To explore association between baseline NLR, PLR, disease activity score and subsequent disease course in patients with AoSD. Materials and Methods: This retrospective cohort study enrolled 61 patients with AoSD and 61 age-matched patients with Fibromyalgia Syndrome (FMS). Pouchot score was specifically used in AoSD patients to assess disease activity based on symptoms, physical examination findings and laboratory results from April 2020 to July 2020. Patients with AoSD were subgrouped into three groups: self-limited; intermittent; and chronic course. The association of NLR and PLR with disease activity score was analysed between groups by using independent samples t-test, Mann-Whitney U test and Kruskal Wallis Variance Analysis. Differences between categorical variables were analysed using chi-square test. A p≤0.05 was considered statistically significant. Results: The mean follow-up of the 61 patients with AoSD was 74 months (range, 14-169). Eighteen patients (29.5%) had a self-limited disease course, nine (14.8%) an intermittent disease course and thirty four (55.7%) a chronic disease course. AoSD patients had significantly higher serum NLR, PLR and lower Mean Platelet Volume (MPV) values than FMS patients {6.68 (1.67-19.7), 1.83 (1.1-4) p=0.0001; 187 (82.9-549), 114 (72-246) p=0.0001; 8.3 (6.4-11.3), 9.3 (7.7-11.7) p=0.0001, respectively}. NLR, PLR and Pouchot score were similar among AoSD subgroups, which were grouped according to disease pattern. The majority of patients in the self-limited and chronic course groups had higher baseline Pouchot score without statistical significance. The NLR and C-Reactive Protein (CRP) were significantly higher in AoSD patients with active disease than inactive disease {7.02 (1.8-19.7), 4.17 (1.67-14.8) p=0.06; 13 (1.9-29.5), 9 (1.6-20.9) p=0.046, respectively)}. Conclusion: High NLR and elevated CRP levels are related to active disease in AoSD patients. Although NLR, PLR and Pouchot score were similar among subgroups, patients with a chronic course or self-limited course had higher NLR values and more active disease at diagnosis compared with patients with an intermittent course.