Risk factors for avascular necrosis among Filipino patients with systemic lupus erythematosus

Aim: To describe the clinical features and risk factors for avascular necrosis (AVN) in a cohort of Filipino patients with systemic lupus erythematosus (SLE). Methods: We reviewed the medical records of SLE patients with a diagnosis of AVN, seen at the University of Santo Tomas (Manila, Philippines) Section of Rheumatology, from 1995 to 2005. The diagnosis of AVN was based on clinical symptoms and confirmed by plain radiographs or magnetic resonance imaging. Possible risk factors for the development of AVN were identified. The clinical data of SLE patients without AVN were also obtained and served as controls. Results: Of the 540 patient charts reviewed, 43 (8.0%) patients (41 female, 2 male) with AVN were included. Out of a total of 66 joints involved, the hip was the most frequently involved. We included 93 SLE patients without AVN who were matched for age, sex and disease duration as the control group. Mean daily prednisone dose (11.9 +/- 7.2 vs 9.3 +/- 6.6 mg, P = 0.023), mean cumulative prednisone-equivalent dose in first month of SLE diagnosis (1.5 +/- 0.8 vs 1.3 +/- 0.8 g, P = 0.011), and total cumulative prednisone-equivalent dose (30.0 +/- 2.7 Vs 20.3 +/- 1.9 g, P = 0.023) were higher in the AVN group than in the controls. Clinical variables significantly associated with AVN included the presence of vasculitis (OR = 4.45, 95% CI 1.65-12.18, P = 0.0007), the use of intravenous pulse steroids (OR = 2.92, 95% CI 1.21-7.08, P = 0.008), and the mean total cumulative prednisone-equivalent dose >= 23.4 g (OR = 2.92, 95% CI 1.3-6.6, P = 0.007). Conclusion: Corticosteroid use and vasculitis were consistent risk factors seen among Filipino SLE patients who developed AVN during the course of their disease.