Neutrophil to Lymphocyte Ratio Predicts Glucocorticoid Resistance in Polymyalgia Rheumatica: A Prospective Study

Background Neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) have been found to correlate with disease activity in several rheumatic diseases, however their clinical and prognostic utility in polymyalgia rheumatica (PMR) remains unclear. This study evaluated the relationship between NLR and PLR, and disease activity and glucocorticoid resistance in PMR. Methods Data for disease activity (PMR-AS) and full blood examination was obtained from a prospective observational cohort comprising newly diagnosed (2012 EULAR/ACR classification criteria), steroid-naïve PMR patients treated with low-dose glucocorticoid therapy (BSR guideline). Glucocorticoid resistance was defined as non-response to initial prednisolone dose (15mg/day) or initial response followed by flare (PMR-AS ≥9.35 or ∆≥6.6) upon weaning prednisolone to 5mg/day. Univariable Bayesian linear regression analysis of the relationship between PMR-AS (baseline and mean) and NLR and PLR was performed. Predictors of glucocorticoid resistance were identified using a multivariable outcome model, with variables chosen based upon Bayesian model selection. Results Of the 32 included patients, 16 (50%) fulfilled the primary outcome measure of glucocorticoid resistance. These participants were older, typically female, and had higher baseline CRP than their glucocorticoid-responsive counterparts. A statistically significant relationship was identified between PMR-AS and both NLR (OR 28.1 [95% CI 1.6 – 54.7]) and PLR (OR 40.6 [95% CI 10.1 – 71.4]) at baseline, with PLR also found to correlate with disease activity during follow-up (OR 15.6 [95% CI 2.7 – 28.2]). Baseline NLR proved to be a statistically significant predictor of glucocorticoid-resistant PMR (OR 14.01 [95% CI 1.49 – 278.06]). Conclusion Baseline NLR can predict glucocorticoid resistance in newly diagnosed PMR patients. Both NLR and PLR may be reliable biomarkers of disease activity in PMR.