Table 3.
Improvement in the discrimination of admission SOFA score for the prediction of hospital mortality by combining SOFA score + CFB at 72 h in all AKI/CKD subgroups
| Model performance metric | AKI+/CKD+ (n =679) | AKI−/CKD+ (n =532) | AKI+/CKD− (n =846) | AKI−/CKD− (n =575) | ||||
|---|---|---|---|---|---|---|---|---|
| ROC AUC (95% CI) | ||||||||
| CFB | 0.70 | (0.65, 0.75) | 0.66 | (0.60, 0.73) | 0.68 | (0.64, 0.72) | 0.65 | (0.58, 0.71) |
| SOFA | 0.69 | (0.64, 0.73) | 0.66 | (0.59, 0.72) | 0.66 | (0.62, 0.70) | 0.63 | (0.56, 0.70) |
| SOFA + CFB | 0.74 | (0.70, 0.79) | 0.71 | (0.64, 0.77) | 0.72 | (0.68, 0.75) | 0.67 | (0.60, 0.73) |
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| ||||||||
|
P-value# SOFA vs SOFA + CFB |
<0.001 | 0.04 | <0.001 | 0.08 | ||||
|
| ||||||||
| Continuous NRIa (95% CI) | 0.53 | (0.37, 0.70) | 0.38 | (0.16, 0.60) | 0.46 | (0.32, 0.61) | 0.35 | (0.13, 0.58) |
| NRI events correctly reclassified | 0.21 | (0.15, 0.27) | 0.01 | (0.002, 0.06) | 0.14 | (0.10, 0.19) | 0.07 | (0.03, 0.15) |
| NRI non-events correctly reclassified | 0.32 | (0.28, 0.36) | 0.37 | (0.33, 0.42) | 0.33 | (0.29, 0.37) | 0.28 | (0.24, 0.32) |
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| ||||||||
| Absolute IDIb (95% CI) | 0.052 | (0.032, 0.072) | 0.058 | (0.028, 0.087) | 0.053 | (0.036, 0.070) | 0.023 | (0.008, 0.037) |
| IDI events | 0.039 | (0.019, 0.079) | 0.047 | (0.019, 0.113) | 0.037 | (0.020, 0.068) | 0.019 | (0.005, 0.076) |
| IDI non-events | −0.013 | (−0.028, −0.006) | −0.010 | (−0.024, −0.004) | −0.016 | (−0.03, −0.009) | −0.003 | (−0.014, −0.001) |
NRI evaluates the incremental effect of adding CFB to SOFA score for the prediction of hospital mortality and quantifies the net number of individuals reclassified correctly using the model of SOFA + CFB compared to SOFA alone with upward reclassification considered beneficial.
IDI measures the increment in the predicted probabilities for the hospital mortality subset and the decrement for the subset without hospital mortality between the model of SOFA + CFB vs SOFA alone.
P-value compares model ROC AUC for SOFA + CFB vs SOFA alone.
AKI =occurrence of acute kidney injury; AUC =area under the curve; CFB =cumulative fluid balance (total fluid input minus output within the first 72 h of ICU admission); CI =confidence interval; CKD =pre-existing CKD; IDI =absolute integrated discrimination improvement; NRI =net reclassification index; ROC =receiver-operating characteristic; SOFA =Sequential Organ Failure Assessment score. NRI and IDI are presented as proportions.