Serum bilirubin level may function as a promising biomarker of interstitial lung disease in primary Sjögren’s syndrome

According to a recent study published in BMC Pulmonary Medicine, serum bilirubin is independently linked to interstitial lung disease (ILD) and hence may act as a potential marker of ILD in primary Sjögren’s syndrome (pSS). 

The retrospective analysis was carried out by Dr. Peng and colleagues on 89 consecutive patients who had been admitted to The Affiliated Hospital of Yoojin Medical University for Nationalities with pSS. The patients were divided into two groups: those with pSS and ILD, and those without ILD. Patients with pSS who had ILD had lower serum bilirubin levels compared to those without ILD (P = 0.010). The researchers noted a negative correlation between serum bilirubin levels and erythrocyte sedimentation rate (ESR) in pSS patients (r = -0.321, P = 0.002). Further analysis using multivariable logistic regression confirmed that serum bilirubin had an independent association with ILD in patients with pSS (OR = 0.841, 95%CI:0.728-0.972, P = 0.019). 

Bilirubin possesses a potent antioxidant capacity, and even minute quantities of bilirubin can significantly contribute to the plasma’s antioxidant capacity by scavenging hydrogen peroxide. In addition, bilirubin demonstrates remarkable anti-inflammatory properties. By inhibiting the infiltration of inflammatory cells and secretion of inflammatory cytokines, bilirubin can ameliorate smoking-induced lung injury. Furthermore, bilirubin can also alleviate bleomycin-induced pulmonary fibrosis by partly inhibiting lung inflammation. Thus, in patients with pSS, bilirubin’s antioxidant and anti-inflammatory effects likely play a protective role against the occurrence and progression of ILD. 

Patients with pSS who have ILD have elevated mortality risk. The identification of bilirubin as a potential biomarker holds promise for early evaluation and detection of ILD in pSS patients, offering a potential avenue for improving the prognosis of individuals with pSS. However, further clinical, and larger cohort studies are necessary to validate and gain a deeper understanding of the present study findings. 

 Reference: Peng YF, Lu FY, Ma LY. Serum bilirubin levels in primary Sjögren’s syndrome: an association with interstitial lung disease. BMC Pulm Med. 2023 Sep 30;23(1):366.