Real-Time Machine Learning Model to Predict Cardiac Arrest Within 12 Hours in Critically Ill Patients (DeepiCARS): A Confirmatory Trial and External Validation

Background/Objectives: Continuous prediction of cardiac arrest in the intensive care unit (ICU) must be judged by considering alarm burden as well as discrimination. We evaluated DeepiCARS (iCARS), an approved recurrent-network and gradient-boosting ensemble, developed at one centre and temporally validated there, predicting in-ICU cardiac arrest within 12 h. Methods: The unchanged model was assessed in a retrospective 1:1 matched confirmatory trial at that centre (214 adults, 107 with arrest), which assigned no intervention and required no registration, and in 30,487 adult ICU admissions at an independent Korean tertiary centre (2010–2021; 2782 with an in-window arrest: 653 with cardiopulmonary resuscitation [CPR] and 2129 deaths without CPR), against seven conventional scores, per subject in the trial and per prediction point externally, on discrimination, sensitivity at matched alarm burden, lead time and calibration. Results: The area under the receiver operating characteristic curve (AUROC) with the extended input (vital signs, Glasgow Coma Scale, age, sex and 21 laboratory values) was 0.9428 (95% confidence interval 0.9102–0.9753) in the trial and 0.9587 (0.9548–0.9626) externally, and with the core (non-laboratory) input 0.9103 (0.8716–0.9490) and 0.9458 (0.9415–0.9500), above every comparator. For arrests with CPR, the external AUROC was 0.8697 (0.8538–0.8854) with the extended input and 0.8425 (0.8264–0.8591) with the core input, above the National Early Warning Score 2 (NEWS2), 0.7157 (0.6987–0.7319), and the Sequential Organ Failure Assessment (SOFA), 0.7424 (0.7205–0.7631). At no greater alarm burden than NEWS2 ≥ 7 and SOFA ≥ 11, iCARS with the extended input detected 37.17 (35.75–38.65) and 30.66 (28.76–32.65) percentage points more of the points preceding an arrest, with median lead times within the 12 h window of 11.42 h and 11.50 h; the score was already above threshold when the window opened in 53.8% and 58.3% of admissions with an arrest, and first crossed it a median of 72.42 h and 80.84 h before the arrest. Conclusions: Evaluated unchanged, the approved model retained high discrimination externally, including for arrests with CPR, and detected more of the points preceding an arrest than conventional scores at no greater alarm burden. No operating threshold is proposed.