Neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) correlate with disease activity in several rheumatic diseases; however, their utility in polymyalgia rheumatica (PMR) remains unclear. This study evaluated their relationship with disease activity and glucocorticoid resistance in PMR.
Data for disease activity (PMR-AS) and full blood examination was obtained from a prospective observational cohort comprising newly diagnosed, steroid-naïve PMR patients treated with low-dose glucocorticoid therapy. Glucocorticoid resistance was defined as non-response to prednisolone 15 mg/d or initial response followed by flare (PMR-AS ≥ 9.35 or ∆ ≥6.6) upon weaning to 5 mg/d. 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 derived from Bayesian model selection.
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 C-reactive protein than their glucocorticoid-responsive counterparts. A statistically significant relationship was identified between PMR-AS and both NLR (odds ratio [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 a statistically significant predictor of glucocorticoid-resistant PMR (OR 14.01; 95% CI 1.49-278.06).
Baseline NLR can predict glucocorticoid resistance in newly diagnosed PMR patients. Both NLR and PLR may be reliable biomarkers of disease activity in PMR.