We sought to develop a simple point score that would accurately capture the risk of hospital death for patients with acute lung injury (ALI).
This is a secondary analysis of data from two randomized trials. Baseline clinical variables collected within 24 hours of enrollment were modeled as predictors of hospital mortality using logistic regression and bootstrap resampling to arrive at a parsimonious model. We constructed a point score based on regression coefficients.
Medical centers participating in the Acute Respiratory Distress Syndrome Clinical Trials network (ARDSnet).
Model development: 414 patients with non-traumatic ALI participating in the low tidal volume arm of the ARDSnet ARMA study. Model validation: 459 patients participating in the ARDSnet ALVEOLI study.
Measurements and Main Results
Variables comprising the prognostic model were: hematocrit <26% (1 point), bilirubin ≥ 2 mg/dl (1 point), fluid balance greater than 2.5 liters positive (1 point), and age (1 point for age 40–64, 2 points for age ≥ 65 years). Predicted mortality (95% confidence interval) for 0, 1, 2, 3, and 4+ point totals was 8% (5–14%), 17% (12–23%), 31% (26–37%), 51% (43–58%), and 70% (58–80%), respectively. There was excellent agreement between predicted and observed mortality in the validation cohort. Observed mortality for 0, 1, 2, 3, and 4+ point totals in the validation cohort was 12%, 16%, 28%, 47%, and 67%, respectively. Compared to the APACHE III score, areas under the receiver operating characteristic curve for the point score were greater in the development cohort (0.72 vs. 0.67, p=0.09) and lower in the validation cohort (0.68 vs. 0.75, p=0.03).
Mortality in ALI patients can be predicted using an index of four readily-available clinical variables with good calibration. This index may help inform prognostic discussions, but validation in non-clinical trial populations is necessary before widespread use.