Determination of serum free light chains as a marker of systemic lupus flare.

Introduction: The aim of this study was to explore the usefulness of the determination of free light chains (FLC) in serum as a biomarker of flare in patients with systemic lupus erythematosus (SLE) and to analyze the differences in their discriminatory capacity with complement C3 and C4.

Methods: This was a prospective cohort study. The definition of flare was based on the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) Flare Index.