Inflammatory anemia may be an indicator for predicting disease activity and structural damage in Chinese patients with rheumatoid arthritis

This study aimed to investigate the relationship of serum hemoglobin (HB) level with disease activity and structural damage in Chinese patients with rheumatoid arthritis (RA).A total of 890 RA patients and 890 normal subjects were enrolled in the case-control study. A HB threshold of 110 g/L (women) and 120 g/L (men) was used to determine anemia. All the patients were divided into three groups: non-anemia group (HB ≥ 120 g/L (male) or 110 g/L (female)), mild anemia group ((90 g/L HB lower limit of normal), and medium to severe anemia group (HB ≤ 90 g/L). Serum HB level and anemia prevalence between RA patients and normal subjects were compared. Associations of HB level with disease activity, structural damage, and function of joint in different groups were also investigated.The average of HB level in RA was (109.08 ± 17.96)g/l, which was lower than that in controls (136.75 ± 14.57)g/l (P 0.001). Anemia was observed in 47% of the RA patients, while prevalence of anemia in control group was only 4.4%. In RA group, percentages of non-anemia, mild anemia, and medium to severe anemia were 47%, 38%, and 15%. Compared with non-anemia RA patients, RA patients with anemia had higher disease activity, severer structural damage and worse function of joint (P 0.001). With the increase of anemia, the disease activity, structural damage, and dysfunction of joints increased significantly (P 0.05-0.001). Linear regression analysis showed that HB level was negatively correlated with disease activity parameters, degree of joint destruction, and function (P 0.05-0.001). Logistic regression indicated that serum HB level was protective factors for disease activity and structural damage in RA (P 0.001).HB level was significantly related to disease activity and structural damage in RA patients.Key Points• Inflammatory anemia was popular (about a half) in patients with RA.• HB level was related to disease activity and structural damage in RA patients.