PD‐1 mRNA expression in peripheral blood mononuclear cells as a biomarker for different stages of primary gouty arthritis

There is currently a lack of biomarkers to assist the diagnosis and prediction of primary gouty arthritis (PG). Therefore, we evaluated the clinical value of programmed cell death protein 1 (PD‐1) mRNA expression in peripheral blood mononuclear cells (PBMCs) of patients with PG. This study included 36 patients with acute phase PG (APPG), 48 with non‐acute phase PG (NAPPG), 42 with asymptomatic hyperuricemia (AH) and 79 normal controls (NCs). PD‐1 mRNA expression levels were detected by qRT‐PCR. PD‐1 mRNA expression was statistically analysed by ANOVA or t tests, while correlations between PD‐1 mRNA and clinical variables were assessed using Pearson correlation tests. Receiver operator characteristic (ROC) curve analysis was used to evaluate the diagnostic value of PD‐1 in different PG stages. PD‐1 mRNA expression was significantly lower in patients with APPG than that in NAPPG, AH and NCs (P < 0.01). Correlation analysis revealed that PD‐1 mRNA levels correlated negatively with T‐score (r = −0.209, P < 0.01). ROC curve analysis showed that serum uric acid (SUA), PD‐1 mRNA and both combined displayed higher diagnostic value in patients with PG, NAPPG and APPG compared to that in NCs and patients with non‐PG arthritis (NPG). Moreover, ROC curve analysis showed that SUA and PD‐1 mRNA had good diagnostic value in APPG, with the greatest diagnostic power when combined. PD‐1 mRNA could be a clinical auxiliary diagnostic biomarker for APPG, and the combined use of PD‐1 mRNA and SUA is better than that of SUA alone.