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Table 2 Overview of the variables used as observed and unobserved confounders

From: Instrumental variable analysis to estimate treatment effects: a simulation study showing potential benefits of conditioning on hospital

Observed confounders GCS motor score
Hypothetically ‘Unobserved’ confounders Pupillary reactivity
TCDB CT classification
  1. Glasgow Coma Scale (GCS) motor score, pupillary reactivity, the Traumatic Coma Data Bank computed tomography (TCDB CT) scan classification, the presence of subarachnoid hemorrhages (SAH) and age
  2. CT classification is based on the Marshall classification