Patient Specific Predictions in the Intensive Care Unit Using a Bayesian Ensemble

Alistair E. W. Johnson*, Nic Dunkley, Louis Mayaud, Athanasios Tsanas, Andrew A. Kramer, Gari D. Clifford

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Introduction: An intensive care unit mortality prediction model for the PhysioNet/Computing in Cardiology Challenge 2012 using a novel Bayesian ensemble learning algorithm is described.

Methods: Data pre-processing was automatically performed based upon domain knowledge to remove artefacts and erroneous recordings, e.g. physiologically invalid entries and unit conversion errors. A range of diverse features was extracted from the original time series signals including standard statistical descriptors such as the minimum, maximum, median, first, last, and the number of values. A new Bayesian ensemble scheme comprising 500 weak learners was then developed to classify the data samples. Each weak learner was a decision tree of depth two, which randomly assigned an intercept and gradient to a randomly selected single feature. The parameters of the ensemble learner were determined using a custom Markov chain Monte Carlo sampler.

Results: The model was trained using 4000 observations from the training set, and was evaluated by the organisers of the competition on two new datasets with 4000 observations each (set b and set c). The outcomes of the datasets were unavailable to the competitors. The competition was judged on two events by two scores. Score 1 was the minimum of the positive predictive value and sensitivity for binary model predictions, and the model achieved 0.5310 and 0.5353 on the unseen datasets. Score 2, a range-normalized Hosmer-Lemeshow C statistic, evaluated to 26.44 and 29.86. The model was re-developed using the updated data sets from phase 2 after the competition, and achieved a score 1 of 0.5374 and a score 2 of 18.20 on set c.

Conclusion: The proposed prediction model performs favourably on both the provided and hidden data sets (set A and set B), and has the potential to be used effectively for patient-specific predictions.

Original languageEnglish
Title of host publication2012 COMPUTING IN CARDIOLOGY (CINC), VOL 39
EditorsA Murray
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Number of pages4
ISBN (Electronic)978-1-4673-2077-1
ISBN (Print)978-1-4673-2076-4
Publication statusPublished - 28 Jan 2013
Event39th Conference on Computing in Cardiology - Krakow, Poland
Duration: 9 Sep 201212 Sep 2012

Publication series

NameComputers in Cardiology Series
ISSN (Print)0276-6574


Conference39th Conference on Computing in Cardiology




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