Background: Hydroxychloroquine (HCQ) has been proposed to be associated with later onset of systemic lupus erythematosus (SLE)¹ and is widely used in patients with primary Sjögren’s syndrome (pSS) which may evolve to SLE.² We want to explore the potentially protective role of HCQ in the development of SLE among patients with pSS.

Objectives: This study was conducted to assess whether exposure to HCQ in pSS patients is associated with a reduction in the development of SLE.

Methods: This retrospective cohort used claims data from the National Health Insurance Registry Database (NHIRD) in Taiwan. Patients with incident Sjögren’s syndrome (SS) from 2000 to 2010 in the Registry of Catastrophic Illness Database (RCIPD) of the NHIRD, which was certified by two rheumatologists, were identified. The date when SS was diagnosed in the RCIPD was defined as the index date. Those who were diagnosed as having SLE, rheumatoid arthritis, polymyositis, dermatomyositis, or systemic sclerosis in the RCIPD before the index date were excluded. Other exclusion criteria included¹ patients who were diagnosed as having SLE in the RCIPD within one year after the index date,² patients who withdrew from the NHIRD within one year after the index date, and³ patients who used oral, intramuscular, or intravenous corticosteroids, methotrexate, azathioprine, leflunomide, sulfasalazine, cyclosporine, tacrolimus, mycophenolate, mercaptopurine, or cyclophosphamide for more than or equal to 90 days within one year before or after the index date. The included SS patients who used HCQ for more than or equal to 90 days within one year after the index date were eligible to HCQ group. The study endpoint was defined as newly-diagnosed SLE in RCIPD or withdraw from NHIRD during the 14 year follow-up period (January 1st, 2000 to December 31st, 2013).

Results: A total of 7004 pSS patients were identified. The mean follow-up time was 6.9 years in the HCQ group (n=4282) and 7.0 years in the non-HCQ group (n=2722). There were 22 newly-diagnosed SLE (0.5%) in the HCQ group and 16 (0.6%) in the non-HCQ group. The overall event rate of SLE was 8.78/10,000 person-years in the HCQ group and 9.83/10,000 person-years in the non-HCQ group (adjusted hazard ratio 0.97, 95% confidence interval 0.50–1.88, in a Cox proportional hazard model).

Conclusions: There is no protective effect of HCQ on the development of SLE in patients with pSS.

References:

1. James JA, Kim-Howard XR, Bruner BF, et al. Hydroxychloroquine sulfate treatment is associated with later onset of systemic lupus erythematosus. Lupus 2007;16:401–409.
2. McDonagh JE, Isenberg DA. Development of additional autoimmune diseases in a population of patients with systemic lupus erythematosus. Ann Rheum Dis 2000;59:230–232.

Disclosure of Interest: None declared

DOI: 10.1136/annrheumdis-2018-eular.3885