Table 3.
ROC–AUC evaluation of biomarker performance on entry a
| AUC | P-value | Upper quartile threshold | Sensitivityb | Specificityb | PPVb | NPVb | |
|---|---|---|---|---|---|---|---|
| Diagnosis of AKI (n=147) | |||||||
| GGT/uCr | 0.59 (0.54–0.65)c | 0.0009 | 25 (Units/l)/mmol/l Cr | 0.37 (0.30–0.45) | 0.80 (0.76–0.84) | 0.42 (0.34–0.50) | 0.76 (0.72–0.80) |
| AP/uCr | 0.45 (0.40–0.50)d | 0.07 | 1.8 (Units/l)/mmol/l Cr | 0.27 (0.20–0.34) | 0.76 (0.72–0.80) | 0.31 (0.23–0.38) | 0.73 (0.69–0.77) |
| CysC/uCr | 0.67 (0.62–0.73) | <0.0001 | 0.17 (mg/l)/mmol/l Cr | 0.40 (0.32–0.48) | 0.81 (0.77–0.85) | 0.45 (0.36–0.53) | 0.78 (0.73–0.82) |
| NGAL/uCr | 0.66 (0.60–0.72) | <0.0001 | 41 (ng/ml)/mmol/l Cr | 0.40 (0.31–0.48) | 0.80 (0.76–0.84) | 0.43 (0.34–0.51) | 0.78 (0.74–0.83) |
| IL-18/uCr | 0.62 (0.56–0.67)e | <0.0001 | 36 (pg/ml)/mmol/l Cr | 0.34 (0.26–0.41) | 0.78 (0.74–0.82) | 0.37 (0.29–0.46) | 0.75 (0.71–0.80) |
| KIM-1/uCr | 0.66 (0.61–0.72) | <0.0001 | 210 (pg/ml)/mmol/l Cr | 0.40 (0.32–0.48) | 0.81 (0.77–0.85) | 0.45 (0.37–0.54) | 0.78 (0.73–0.82) |
| Prediction of dialysis in 7 days (n=19) | |||||||
| GGT/uCr | 0.60 (0.46–0.74)f | 0.15 | 25 (Units/l)/mmol/l Cr | 0.28 (0.07–0.48) | 0.75 (0.71–0.79) | 0.04 (0.01–0.07) | 0.97 (0.95–0.98) |
| AP/uCr | 0.63 (0.49–0.77) | 0.07 | 1.8 (Units/l)/mmol/l Cr | 0.61 (0.39–0.84) | 0.76 (0.73–0.80) | 0.08 (0.04–0.13) | 0.98 (0.97–1.00) |
| CysC/uCr | 0.71 (0.57–0.84) | 0.003 | 0.17 (mg/l)/mmol/l Cr | 0.56 (0.33–0.79) | 0.76 (0.72–0.80) | 0.08 (0.03–0.12) | 0.98 (0.97–0.99) |
| NGAL/uCr | 0.79 (0.65–0.94) | <0.0001 | 41 (ng/ml)/mmol/l Cr | 0.64 (0.39–0.89) | 0.76 (0.72–0.80) | 0.07 (0.03–0.12) | 0.99 (0.97–1.00) |
| IL-18/uCr | 0.73 (0.59–0.86) | 0.001 | 36 (pg/ml)/mmol/l Cr | 0.67 (0.45–0.88) | 0.76 (0.73–0.80) | 0.09 (0.04–0.14) | 0.98 (0.97–1.00) |
| KIM-1/uCr | 0.62 (0.48–0.76)g | 0.10 | 210 (pg/ml)/mmol/l Cr | 0.44 (0.21–0.67) | 0.76 (0.72–0.79) | 0.06 (0.02–0.10) | 0.97 (0.96–0.99) |
| Prediction of death in 7 days (n=53h) | |||||||
| GGT/uCr | 0.65 (0.56–0.73) | 0.003 | 25 (Units/l)/mmol/l Cr | 0.42 (0.28–0.55) | 0.77 (0.73–0.81) | 0.17 (0.10–0.23) | 0.92 (0.89–0.95) |
| AP/uCr | 0.61 (0.53–0.70) | 0.008 | 1.8 (Units/l)/mmol/l Cr | 0.43 (0.30–0.57) | 0.77 (0.73–0.81) | 0.18 (0.11–0.24) | 0.92 (0.90–0.95) |
| CysC/uCr | 0.66 (0.58–0.75) | 0.0001 | 0.17 (mg/l)/mmol/l Cr | 0.42 (0.28–0.55) | 0.77 (0.73–0.81) | 0.17 (0.10–0.23) | 0.92 (0.89–0.95) |
| NGAL/uCr | 0.66 (0.57–0.74) | 0.0002 | 41 (ng/ml)/mmol/l Cr | 0.47 (0.33–0.61) | 0.78 (0.74–0.81) | 0.20 (0.13–0.27) | 0.93 (0.90–0.95) |
| IL-18/uCr | 0.68 (0.60–0.76) | <0.0001 | 36 pg/ml)/mmol/l Cr | 0.55 (0.41–0.68) | 0.78 (0.75–0.82) | 0.22 (0.15–0.29) | 0.94 (0.92–0.96) |
| KIM-1/uCr | 0.56 (0.47–0.64)i | 0.17 | 210 (pg/ml)/mmol/l Cr | 0.34 (0.21–0.47) | 0.76 (0.72–0.80) | 0.14 (0.08–0.20) | 0.91 (0.88–0.94) |
Abbreviations: AKI, acute kidney injury; AP, alkaline phosphatase; AUC, area under the receiver operator characteristic (ROC) curve; CysC, cystatin C; GGT, γ-glutamyltranspeptidase; IL-18, interleukin-18; KIM-1, kidney injury molecule-1; NGAL, neutrophil-gelatinase-associated lipocalin; NPV, negative predictive value; PPV, positive predictive value; uCr, urinary creatinine.
n=528. The 95% confidence intervals for all values are shown in brackets.
Calculated using the threshold value of the upper quartile for each biomarker as the cutoff. For the model, the upper quartile shown is the upper quartile of the probability calculated by the model of having the event.
AKI: significantly lower than the AUCs for CysC/uCr and NGAL/uCr.
AKI: significantly lower than all the other biomarkers.
AKI: significantly lower than the AUC for CysC/uCr.
Dialysis: significantly lower than the AUC for NGAL/uCr.
Dialysis: significantly lower than the AUC for IL-18/uCr.
One patient who died was anuric on entry and no urinary biomarkers data were obtained; therefore, n=53 not n=54.
Death: significantly lower than the AUC for CysC/uCr, NGAL/uCr, and IL-18/uCr.