The clinical value of changes in NGAL, combined with WRF, was examined by comparing clinical outcomes between patients with and without WRF, and with a similar rise in NGAL on day 4. This was defined as an increase of ≥1 SD (≥88 ng/mL) in NGAL (n = 83), as the SD for creatinine change by day 4 was about 0.3 mg/dL, resembling the definition of WRF. The Kaplan-Meier curve is displayed in Figure 4, showing a significantly increased risk of mortality, only if both markers rose significantly (p-value for WRF with NGAL increase ≥88 ng/mL versus the other three groups = 0.007). Patients with ≥1 SD rise in NGAL had significantly higher creatinine at baseline than those who did not (p < 0.05), but similar levels, irrespective of whether WRF developed (1.8 vs. 1.7 mg/dL with vs. without WRF, p = 0.59). Baseline characteristics in this small subgroup did not differ significantly based on WRF status.