A simple severity of disease index for systemic lupus erythematosus.

Although indices of activity for systemic lupus erythematosus have been developed and validated, a disease staging system requires the measurement of severity as well. We have constructed such a scale, the Lupus Severity of Disease Index (Lupus SDI). Accepted clinical, pathologic and physiologic classification schemes were employed to validate this index at two separate research institutions. The Lupus SDI allows homogenization of patient populations for the purposes of research and, possibly, for case mix adjustment.