Laboratory assessment
insufficiency
Anti-nuclear antibody (ANA) was tested by indirect immunofluorescence (Hep 2010, EUROImmune, Lubeck, Germany). Serum complements C3 and C4 were measured using BN™ II System nephelometer (SIEMENS Healthliners). Anti-double stranded DNA (anti-dsDNA) was measured using ELISA (EUROImmune, Lubeck, Germany). In a subset of patients, interferon-related proteins galectin 9 and CXCL 10 were measured using ELISA (R&D system, USA). Plasma vitamin D levels were measured using chemiluminescence (COBAS, Roche Diagnostics GmbH, Mannheim, Germany). Vitamin D levels of ≤ 20 ng/ ml was defined as deficiency, > 20 to < 30 ng/ml as insufficiency and ≥ 30 ng/ml as sufficient [