The 'availability' bias: underappreciated but with major potential implications.

Area of Science:

• Clinical research methodology
• Medical bias studies

Background:

• Numerous biases can compromise study integrity and favor specific outcomes.
• Availability bias, a significant yet underappreciated bias, arises when study interventions are accessible to clinicians outside the trial setting.

Purpose of the Study:

• To highlight the underappreciated impact of availability bias on clinical trial outcomes.
• To explain the mechanism by which availability bias can favor control arms in clinical trials.

Main Methods:

• Conceptual analysis of bias in clinical trial design and execution.
• Examination of clinician behavior and its influence on patient enrollment.

Main Results:

• Availability bias can lead clinicians to enroll patients unlikely to benefit from the intervention into trials.
• This selective enrollment can create an imbalance, favoring the control arm over the intervention arm.
• Clinician equipoise may not align with study investigator equipoise, further complicating trial analysis.

Conclusions:

• Availability bias poses a significant threat to the internal validity of clinical trials.
• This bias can systematically affect the interpretation of trial results and subsequent systematic reviews.
• Addressing availability bias is crucial for ensuring the reliability of clinical evidence.