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Comment & Response
February 18, 2020

Unmeasured Confounding in Observational Studies of Management of Cerebellar Intracranial Hemorrhage

Author Affiliations
  • 1University Neurosurgical Center Holland, Leiden University Medical Center, Leiden, the Netherlands
  • 2Division of Anaesthesia, University of Cambridge, Cambridge, England
  • 3Center for Medical Decision Sciences, Erasmus MC–University Medical Center Rotterdam, Rotterdam, the Netherlands
JAMA. 2020;323(7):665-666. doi:10.1001/jama.2019.20851

To the Editor In a propensity score–matched cohort of 578 patients from 4 observational cohort studies, Dr Kuramatsu and colleagues showed that evacuation of medium-sized intracerebellar hematomas (approximate volume, 20 cm3) was not associated with better functional outcome.1 Assessing treatment effectiveness in observational data is challenging because treatment decisions are based on patient characteristics that also are typically predictive of outcome, causing confounding by indication. Although the authors addressed this potential bias with propensity scores, we would like to emphasize the possibility of residual confounding.

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