Research Reports - Multivariate outcome prediction in traumatic brain injury with focus on laboratory values
J Neurotrauma. 2012 Sep 20
Nelson DW, Rudehill A, Maccallum RM, Holst A, Wanecek M, Weitzberg E, Bellander BM
Traumatic brain injury (TBI) is a major cause of morbidity and mortality.
Identifying factors relevant to outcome can provide a better understanding of TBI
pathophysiology, in addition to aiding prognostication. Many common laboratory
variables have been related to outcome but may not be independent predictors in a
multivariate setting. 757 patients were indentified in the Karolinska TBI
database and had retrievable early laboratory variables. These were analyzed
towards a dichotomized Glasgow Outcome Scale (GOS) with logistic regression and
relevance vector machines, a non-linear machine learning method, univariately and
controlled for the known important predictors in TBI outcome: age, Glasgow Coma
Score (GCS), pupil response and Computed Tomography (CT) score. Accuracy was
assessed with Nagelkerke's pseudo R2. Of the 18 investigated laboratory variables
15 were found significant (p<0.05) towards outcome in univariate analyses. In
contrast, when adjusting for other predictors few remained significant.
Creatinine was found an independent predictor of TBI outcome. Glucose, albumin
and osmolarity levels were also identified as predictors, depending on analysis
method. A worse outcome related to increasing osmolarity may warrant further
study. Importantly, hemoglobin was not found significant when adjusted for
post-resuscitation GCS as opposed to an admission GCS, and timing of GCS can thus
have a major impact on conclusions. In total, laboratory variables added an
additional 1.3-4.4 % to pseudo R2.