Rotem Lehrer N.1, Springer S.2, Singer N.2, Ofri R.2
1Hadassah-Hebrew University Medical Center, Physiotherapy, Jerusalem, Israel, 2Ariel University, Department of Physical Therapy, Ariel, Israel

Background: The role of cognitive biases and their effect on wide-ranging aspects of medicine has become the focus of a growing body of research; yet, their effect in physical therapy is not well established.

Purpose: To test whether anchoring information provided to physical therapists prior to a wrist range of motion (ROM) test may induce bias in the measurement.

Methods: A total of 120 physical therapists participated in the study. Participants were asked to measure passive wrist extension ROM of a 65 years old female with no history of injury to the upper limb using a universal goniometer. Before initiating the measurement some participants received a clinical description which included ´sham´ information about the patient’s health history. Three groups were differentiated according to the provided clinical content: no bias (n=38), medium bias (n=41), and substantial bias (n=41). ANCOVA was applied to test for differences between the three groups while controlling for any potential gender and experience effects.

Results: The ANCOVA yielded a significant group effect (p=0.009), with no significant effect for gender and experience. The adjusted mean wrist ROM was 80.2 for the non- bias group, 74.5 for the moderate bias group, and 72.4 for the substantial group. Post- Hoc tests demonstrated significant difference only between the group with no bias and the substantial bias group, p=0.009.

Conclusion(s): Anchoring information apparently affected the outcome of a test considered as an objective examination in physical therapy. While this study explored the influence of anchoring information on a technical skill, it suggests that many other sources might bias the clinical reasoning and decision making processes.

Implications: Clinicians should be aware of the effect of cognitive bias, even in "objective" measures, and consider employing de-biasing strategies.

Funding acknowledgements: None.

Topic: Musculoskeletal: upper limb

Ethics approval: Review Board of the Physical therapy Department at Ariel University, Israel

All authors, affiliations and abstracts have been published as submitted.

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