Referral bias in aneurysmal subarachnoid hemorrhage

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Double Direct Injection of Blood into the Cisterna Magna as a Model of Subarachnoid Hemorrhage
10:34

Double Direct Injection of Blood into the Cisterna Magna as a Model of Subarachnoid Hemorrhage

Published on: August 30, 2020

J P Whisnant1, S E Sacco, W M O'Fallon

  • 1Department of Health Sciences Research and Neurologic Surgery, Mayo Clinic, Rochester, Minnesota.

Journal of Neurosurgery
|May 1, 1993
PubMed

Insights

Referral bias significantly impacts survival rates in subarachnoid hemorrhage (SAH) patients. Community SAH patients had lower survival than referred patients due to selection bias, not treatment differences.

Area of Science:

  • Neurosurgery
  • Neurology
  • Public Health

Background:

  • Subarachnoid hemorrhage (SAH) poses significant mortality risks.
  • Referral bias may influence observed survival rates in SAH patient cohorts.
  • Understanding referral bias is crucial for accurate SAH outcome assessment.

Purpose of the Study:

  • To evaluate the impact of referral bias on survival outcomes in patients with subarachnoid hemorrhage (SAH).
  • To compare survival rates between community-based and referred SAH patients treated in the same setting.

Main Methods:

  • Comparative analysis of 49 community SAH patients versus 328 referred SAH patients.
  • Differential survival analysis comparing surgically treated referral patients with those awaiting surgery at specific time intervals (Days 1-3, 4-10, 11-15).
  • Identification of independent prognostic factors for survival in referral SAH patients.

Main Results:

  • A significant difference in 30-day survival rates was observed: 83% for referral patients versus 59% for community patients, with most divergence by Day 2.
  • Clinical grade, coma, time to referral, diastolic blood pressure, and age were independent predictors of survival in referral patients.
  • Patients undergoing surgery had higher 1-year survival rates than those awaiting surgery; early and late surgery showed similar 1-year survival.

Conclusions:

  • Referral bias inflates survival rates in SAH cohorts, as critically ill or deceased patients are less likely to be referred.
  • The observed survival advantage in referred SAH patients is attributable to selection bias, not necessarily superior treatment.
  • Differential survival analysis offers a novel method for estimating survival in treated and untreated SAH populations.

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