Responsiveness of clinical and ultrasound outcome measures in musculoskeletal systemic lupus erythematosus

Objective

To assess the responsiveness of clinical outcome measures in musculoskeletal SLE compared with ultrasound.

Methods

A prospective pilot study was conducted in consecutive SLE patients with inflammatory musculoskeletal symptoms. Clinical assessments including SLEDAI, BILAG, 28-tender and swollen joint counts, physician and patient VAS and ultrasound were performed at 0, 2 and 4 weeks following 120mg intramuscular methylprednisolone acetate. Responsiveness was analysed using changes and effect sizes using Cohen’s criteria.

Results

20 patients were recruited. 15/20 had clinical swelling at baseline. All clinical and US parameters were significantly improved at week 4 (all p≤0.01). Musculoskeletal-BILAG score improved in 16/20. Musculoskeletal-SLEDAI improved in 7/20. SRI-4 criteria were assessed in 19 patients with SLEDAI>= 4 at baseline met in 9/19 at 4 weeks. Effect sizes at 4 weeks were large (>0.5) for US, physician VAS and BILAG and medium (>0.3) for joint counts and SLEDAI. Large effect sizes for improvement in US GS and PD were observed in both SRI responders (r=-0.51 and -0.56 respectively) and non-responders (r=-0.62 and -0.59) at 4 weeks.

Conclusions

This is the first study to measure the responsiveness of clinical outcome measures in musculoskeletal SLE against an objective inflammation measure. BILAG and physician VAS were the most responsive clinical instruments. US was highly responsive in musculoskeletal SLE, while SLEDAI and joint counts appeared suboptimal for detection of improvement. These results suggest that clinical trials based on the SLEDAI and SRI-4 may underestimate the efficacy of therapy in SLE