Plasma NGAL was not independently prognostic for death or rehospitalization. Our findings suggest elevated baseline NGAL levels, and large increases in NGAL do confer additional risk for patients who develop WRF (although the clinical relevance of these findings—given the lack of independent prognostic value for NGAL, the small numbers of patients with NGAL increases, and the post-hoc nature of our analyses—remains to be established).