Jing XIE1, Zhencheng ZHANG1, Yan LIANG2, Zaixing YANG1

1Department of Laboratory Medicine,Huangyan Hospital of Wenzhou Medical University, Taizhou First People’s Hospital, Taizhou, China
2Department of Laboratory Diagnostics, Changzheng Hospital, Second Military Medical University, Shanghai, China

Keywords: Bilirubin, disease activity, primary Sjögren's syndrome

Abstract

Objectives: This study aims to determine the serum bilirubin levels in primary Sjögren's syndrome (pSS) patients and to explore clinical significance of bilirubin in pSS.

Patients and methods: Retrospective analysis of electronic medical records was performed in 97 pSS patients (12 males, 85 females; mean age 54±15 years; range, 15 to 91 years) and 100 healthy controls (17 males, 83 females; mean age 51±14 years; range, 25 to 75 years). Serum bilirubin and other variables were compared between pSS patients and healthy controls. The European League Against Rheumatism Sjögren's syndrome disease activity index (ESSDAI) was used to assess the disease activity of pSS, and ESSDAI ≥5 was defined as moderate to high activity. The relationship between bilirubin and ESSDAI was analyzed by Spearman's correlation analysis and multivariable logistic regression.

Results: The median level of serum bilirubin was 9 μmol/L (interquartile range (IQR), 7-13 μmol/L) in pSS patients, much lower than healthy controls (median, IQR, 13, 10-18 μmol/L) (p<0.001). It was positively correlated with age (r=0.255, p=0.012), but negatively with immunoglobulin (Ig) A (r=-0.314, p=0.003), IgG (r=-0.265, p=0.015), erythrocyte sedimentation rate (r=-0.309, p=0.002) and ESSDAI (r=-0.342, p=0.001). Multivariate analysis revealed that increased bilirubin was independently associated with decreased risk of moderate to high disease activity (odds ratio, 95% confidence interval: 0.852, 0.730-0.955).

Conclusion: Serum bilirubin is decreased in pSS patients and may be a useful biomarker for reflecting pSS disease activity.