Operator bias refers to systematic differences in outcomes that arise due to variations in the skill, experience, decision-making, or preferences of the individual performing a procedure or intervention.
⚠️ Key Characteristics
Outcomes influenced by who performs the procedure, not just what is done
Particularly relevant in surgical and interventional studies
Often unacknowledged in retrospective analyses
Can confound comparisons between techniques or centers
🧪 Example in Neurosurgery
A high-volume vascular neurosurgeon may achieve better outcomes with clipping than general neurosurgeons, skewing results in favor of surgery when comparing to endovascular treatment performed by less experienced interventionalists.
📉 Why It Matters
Distorts the apparent efficacy or safety of a procedure
Makes multicenter or multitechnique comparisons unreliable
Introduces hidden bias in non-randomized studies
✅ Best Practice
Report operator volume and experience
Perform stratified or sensitivity analyses by operator
Acknowledge as a potential confounder in observational studies