Referral bias in aneurysmal subarachnoid hemorrhage

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.