Abstract: Objective To investigate the diagnostic value and clinical significance of plasma heparin-binding protein (HBP) in patients with rheumatoid arthritis (RA) complicated by bacterial infection. Methods A total of 122 RA patients, 23 patients with simple bacterial infection, and 60 healthy people who underwent physical examination during the same period were included as the research subjects, including 42 patients with RA complicated with bacterial infection, 39 patients in the active RA group, and 41 patients in the RA remission group. The concentration of HBP in venous blood was measured by transmission immunoturbidimetric assay, and its correlation with white blood cells (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) was evaluated. The Kruskal-Wallis H test was used for comparison between different groups, and Spearman for continuous variable correlation analysis; and then the receiver operating characteristic (ROC) curve was drawn to evaluate the sensitivity and specificity of HBP in the differential diagnosis of RA patients with bacterial infection. Results The HBP in the group of RA complicated with bacterial infection was 63.3 (36.83~123) ng/mL, higher than 17 (14~21.6) ng/mL (P<0.01) in the active RA group, 8.3 (6.65~9.6) ng/mL (P<0.01) in the RA remission group, and 7.4 (5.63~8.8) ng/mL (P<0.01) in the healthy control group,compared with 68.70 (42.10~100.60) ng/mL in the simple bacterial infection group, there was no significant difference (P>0.05). The active RA group had higher HBP than the RA remission group (P<0.01) and the healthy control group (P<0.01), there being no statistical difference between the RA remission group and the healthy control group (P>0.05). The level of HBP in the group of RA complicated with bacterial infection was positively correlated with CRP (r=0.332, P<0.05), and the level of HBP in active RA group was positively correlated with CRP and disease activity (DAS28) (r=0.582, P<0.01; r=0.461, P<0.05), with no correlation in the levels of HBP and WBC and ESR between the two groups (P>0.05). The ROC curve showed that when the HBP level was 24.55 ng/mL, it was the best threshold for diagnosing bacterial infection in RA patients, with a sensitivity of 92.9% and a specificity of 84.6%. Conclusion HBP could be a sensitive and specific index for the differential diagnosis of RA complicated with bacterial infection and at the active stage.

Key words: Heparin-binding protein, Rheumatoid arthritis, C-reactive protein, Erythrocyte sedimentation rate, Bacterial infections