Serum Beta 2-Microglobulin/Cystatin C Index: A Useful Biomarker in Lupus Nephritis?

Background: Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease with frequent flares. Our aim was to evaluate the beta 2-microglobulin/cystatin C (beta 2M/CysC) index versus other markers as a predictor factor for assessment of SLE reactivation. Methods: We prospectively analyzed 42 patients with lupus nephritis. Disease activity was classified using SLEDAI-2K and BILAG. Routine renal function and laboratory markers of SLE activity were performed, as well as serum beta 2M (S beta 2M)/serum CysC (SCysC) and S beta 2M/serum creatinine (SCreat) indexes determinations. Results: The 42 enrolled patients had a mean age of 37.7 +/- 13.1 years, 88% were female and 67% Caucasians; mean estimated glomerular filtration rate was 61.9 +/- 20.0 ml/min/1.73m(2). There was a strong correlation between SCreat versus SCysC (r = 0.887), SCreat versus S beta 2M (r = 0.865), and SCysC versus S beta 2M (r = 0.880). Multivariate analysis showed that the S beta 2M/SCreat index is a prognostic factor predicting active lupus nephritis. Conclusion: As SCysC is a good marker of renal function, it would be expected that the S beta 2M/SCysC index could be a better indicator of renal activity than S beta 2M/SCreat, but in the present study it did not add relevant clinical information in the assessment of renal activity in SLE. Copyright (C) 2012 S. Karger AG, Basel