What is an example of anchoring bias in medicine?

Anchoring Bias in Medicine: Definition and Examples

Anchoring bias occurs when clinicians rely too heavily on initial information received about a patient, failing to adequately adjust their diagnostic reasoning when new information becomes available. 1 This cognitive bias can significantly impact clinical decision-making, leading to diagnostic errors and potentially harmful patient outcomes.

Understanding Anchoring Bias in Clinical Practice

Anchoring bias is one of the most common cognitive biases affecting medical decision-making. It stems from our tendency to use "System 1" thinking—fast, intuitive pattern recognition—rather than the more deliberate, analytical "System 2" thinking 2. When clinicians anchor on initial information, they may:

• Give disproportionate weight to the first piece of information received
• Fail to adequately adjust their diagnostic reasoning when presented with new, contradictory evidence
• Maintain initial impressions despite evidence suggesting alternative diagnoses

Real-World Examples of Anchoring Bias

Example 1: Missed Diagnosis in Chronic Pain

A 57-year-old man with a 3-year history of unexplained right thigh pain was repeatedly assessed by multiple specialists who found no cause for his pain. The patient was ultimately referred to a physiatry clinic for management of presumed non-organic pain. Only when a physician thoroughly reconsidered possible diagnoses, setting aside previous assessments, was hip synovial osteochondromatosis discovered as the true cause of symptoms 3.

Example 2: Delayed Pulmonary Embolism Diagnosis

A recent large-scale study of 108,019 patients with congestive heart failure (CHF) presenting with shortness of breath found that when CHF was mentioned in the triage documentation before physicians saw the patient, there was:

• 4.6 percentage point reduction in pulmonary embolism (PE) testing
• 15.5 minute delay in PE testing when it was ordered
• 0.15 percentage point lower likelihood of PE diagnosis in the ED

This demonstrates how physicians anchored on the initial CHF information, potentially missing or delaying critical PE diagnoses 4.

Example 3: Self-Perception of Risk

Patients' self-perception of risk before a clinical discussion has an "anchoring effect" that pulls their risk estimate in the direction of their preformed opinion, affecting their understanding of medical information and potentially their treatment decisions 1.

Factors Contributing to Anchoring Bias

1. Time constraints: Rushed decisions in busy clinical settings promote reliance on System 1 thinking 2
2. Fatigue: Cognitive performance decreases with physician fatigue 2
3. Complexity: Multiple variables in medical decision-making make it difficult to consider all possibilities 2
4. Overconfidence: Physicians routinely underestimate the need to intensify therapy and overestimate their guideline adherence 2

Strategies to Mitigate Anchoring Bias

For Individual Clinicians:

• Metacognition: Think about your thinking and develop awareness of your reasoning process 2
• Deliberate pausing: Override System 1 thinking by deliberately pausing to engage System 2 analytical thinking 2
• Explicit reasoning: Articulate your reasoning explicitly in clinical notes or presentations 2
• Consider alternatives: Deliberately consider reasonable alternative diagnoses before settling on a conclusion 2

For Healthcare Systems:

• Error reporting systems: Implement voluntary, blame-free reporting systems 2
• Discrepancy meetings: Review and learn from errors collectively 2
• Quality control: Establish audit standards to improve diagnostic accuracy 2
• Decision support tools: Use paper or computer-based instruments designed to support shared decision-making 1

High-Risk Scenarios for Anchoring Bias

Be particularly vigilant for anchoring bias in these situations:

• Patients with multiple prior evaluations for unexplained symptoms
• Referrals with strong diagnostic labels attached
• Complex patients with multiple comorbidities
• Time-pressured environments like emergency departments
• Handoffs between providers where initial impressions may be transmitted

Conclusion

Anchoring bias is pervasive in medical decision-making and can lead to significant diagnostic errors. By understanding this cognitive pitfall and implementing specific strategies to combat it, clinicians can improve diagnostic accuracy and ultimately enhance patient outcomes.