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Anchoring Bias With Critical Implications
PERIOPERATIVE GRAND ROUNDS
Anchoring Bias With Critical Implications THE CASE A 61-year-old man with a history of stroke went to his primary care physician (PCP) for burning pain and numbness in his left foot that he had experienced for one month. He showed loss of sensation in his left knee and a foot drop secondary to his prior stroke. His pulses were intact with no other abnormalities noted. The PCP diagnosed the patient’s pain and numbness as peripheral neuropathy and referred him to podiatry. The patient went to his PCP four more times and twice to urgent care with left foot pain. Each time he was referred to podiatry, where he never went. At no visit was a complete extremity examination performed, and the complaint was repeatedly attributed to the original diagnosis of peripheral neuropathy. After several visits during a two-month period, the patient went to the emergency department. His left lower leg was dusky in color with extreme tenderness to palpation and his pulses could not be palpated. A computed tomography angiogram revealed complete occlusion of the left superficial femoral artery secondary to atherosclerotic peripheral arterial disease, which required emergent bypass surgery. Because of ischemia of his leg, he developed several infections postoperatively and ultimately required an above-the-knee amputation. Vascular surgeons believed the patient’s chronic burning pain was because of progressive peripheral arterial disease and not peripheral neuropathy.
DISCUSSION In this case, despite repeated encounters with health care providers, the patient’s severe peripheral arterial disease was misdiagnosed, resulting in a serious adverse event. The case demonstrates errors because of diagnostic reasoning. Diagnostic errors are common. For every 1,000 primary care visits, there are approximately 20 diagnostic errors, from which one patient will seek unplanned medical help within two weeks.1 Approximately 27,000 hospital admissions per year in the United States are because of missed or delayed diagnoses in the ambulatory care setting,2 and 150,000 or more patients experience diagnosis-related harm on an annual basis.3 Also,
adverse events related to misdiagnosis are more likely to be judged preventable (ie, 80% of cases) than other types of adverse events such as medication errors (ie, 25% to 50% of cases).4 Approximately 75% of diagnostic errors have a cognitive component.5 Two cognitive components are the tendency to seek only as much information as necessary for an initial clinical impression and the tendency to stick with the initial impression even if new information becomes available. Premature closure is the failure to consider alternative diagnoses after the initial impression is formed. In this case, the first diagnostic misstep was failure to include peripheral arterial insufficiency in the initial diagnostic impression. In patients with foot pain, 15% have peripheral arterial insufficiency, so this diagnosis should be considered in every patient with this clinical presentation.6 Premature closure is exacerbated by anchoring, the tendency for clinicians to stick with the initial impression even as new information becomes available. This patient presented six times during two months with worsening symptoms, yet the diagnostic impression did not change and the management plan was simply repeated. Progressive severe unilateral foot pain should have launched an exploration of other possibilities because most neuropathy pain is bilateral. continued on page 631 This content is adapted from AHRQ WebM&M (Morbidity & Mortality Rounds on the Web) with permission from the Agency for Healthcare Research and Quality. The original commentary was written by Edward Etchells, MD, MSc, and was adapted for this article by Nancy J. Girard, PhD, RN, FAAN, consultant/owner, Nurse Collaborations, Boerne, TX. (Citation: Etchells E. Anchoring bias with critical implications. AHRQ WebM&M [serial online]. http:// webmm.ahrq.gov/case.aspx?caseID¼350. Published June 2015. Accessed February 22, 2016.) Dr Girard has no declared affiliation that could be perceived as posing a potential conflict of interest in the publication of this article. http://dx.doi.org/10.1016/j.aorn.2016.03.012 ª AORN, Inc, 2016
658 j AORN Journal
www.aornjournal.org
June 2016, Vol. 103, No. 6
continued from page 658 A number of cognitive biases contribute to anchoring. The first is confirmation bias, the tendency to selectively seek information that supports initial impressions. Confirmation bias can be reduced by being receptive to new information, such as from the history or physical examination, which could lead to an alternate diagnosis. A second bias is the tendency to overvalue irrelevant information. A third bias, anchoring bias, is inadequate adjustment of probabilities as new disconfirming information becomes available.7 Fourth, clinicians tend to stick with initial impressions as the number of new possible alternative diagnoses increases, referred to as status quo bias. Finally, framing effects can significantly influence diagnostic thinking when forming or revising diagnostic impressions. The framing effect is the tendency to be affected by how information is presented. Framing difficult cases without diagnostic labels and with appropriate uncertainty could reduce anchoring. Despite some limitations in research data, several cognitive- and system-based interventions hold promise for helping to prevent diagnostic errors, such as cognitive awareness. Awareness of cognitive biases and their contribution to diagnostic errors might help clinicians avoid such errors. Improving cognitive awareness could begin with efforts to teach trainees and practicing clinicians about the diagnostic thinking process and could continue through teamwork and case discussions. System-based tools might have improved the results of this case. Structured diagnostic assessments can be augmented by systems that provide guidance about a particular clinical decision at the point of care. For example, such decision support systems could ensure that symptoms of disease are considered and the specificity of common diagnostic tests is available.8 In this case, decision support might have helped the clinician identify arterial disease as a consideration or displayed the evidence to ensure the correct interpretation of the peripheral arterial examination. Computer-assisted diagnostic expert systems are designed to help avoid diagnostic errors.9 For this case, a computer-assisted diagnosis program was provided with the terms “pain left foot, numbness left foot, foot drop, loss of sensation left leg.” The program offered five diagnostic possibilities, including thromboangiitis obliterans, which might have prompted the clinician to consider vascular causes of the patient’s symptoms.
www.aornjournal.org
Perioperative Grand Rounds
In this case, several providers succumbed to common cognitive biases that led to premature closure as well as anchoring on the diagnosis of peripheral neuropathy. More formal education, case conferences, real-time decision support, or application of a computerized diagnostic aid might have prevented this error and the subsequent adverse event.
PERIOPERATIVE POINTS Anchoring is the tendency to stick with initial impressions even as new information becomes available, and this tendency can pose clinical risks. Anchoring could be reduced if clinicians o actively seek information that could refute the current provisional diagnosis; o avoid premature diagnostic labeling and share uncertainty; and o use system-based interventions such as structured diagnostic assessments, diagnostic decision support, and computerized expert diagnostic systems.
References 1. Singh H, Giardina TD, Meyer AN, Forjuoh SN, Reis MD, Thomas EJ. Types and origins of diagnostic errors in primary care settings. JAMA Intern Med. 2013;173(6):418-425. 2. Woods DM, Thomas EJ, Holl JL, Weiss KB, Brennan TA. Ambulatory care adverse events and preventable adverse events leading to a hospital admission. Qual Saf Health Care. 2007; 16(2):127-131. 3. Newman-Toker DE, Makary MA. Measuring diagnostic errors in primary care: the first step on a path forward. Comment on “Types and origins of diagnostic errors in primary care settings.” JAMA Intern Med. 2013;173(6):425-426. 4. Leape LL, Brennan TA, Laird N, et al. The nature of adverse events in hospitalized patients. Results of the Harvard Medical Practice Study II. N Engl J Med. 1991;324(6):377-384. 5. Schiff GD, Hasan O, Kim S, et al. Diagnostic error in medicine: analysis of 583 physician-reported errors. Arch Intern Med. 2009; 169(20):1881-1887. 6. Dunn JE, Link CL, Felson DT, Crincoli MG, Keysor JJ, McKinlay JB. Prevalence of foot and ankle conditions in a multiethnic community sample of older adults. Am J Epidemiol. 2004;159(5):491-498. 7. Tversky A, Kahneman D. Judgment under uncertainty: heuristics and biases. Science. 1974;185(4157):1124-1131. 8. McDonald KM, Matesic B, Contopoulos-Ioannidis DG, et al. Patient safety strategies targeted at diagnostic errors: a systematic review. Ann Intern Med. 2013;158(5 pt 2):381-389. 9. Graber ML, Mathew A. Performance of a web-based clinical diagnosis support system for internists. J Gen Intern Med. 2008; 23(suppl 1):37-40.
AORN Journal j 631
Anchoring Bias With Critical Implications THE CASE A 61-year-old man with a history of stroke went to his primary care physician (PCP) for burning pain and numbness in his left foot that he had experienced for one month. He showed loss of sensation in his left knee and a foot drop secondary to his prior stroke. His pulses were intact with no other abnormalities noted. The PCP diagnosed the patient’s pain and numbness as peripheral neuropathy and referred him to podiatry. The patient went to his PCP four more times and twice to urgent care with left foot pain. Each time he was referred to podiatry, where he never went. At no visit was a complete extremity examination performed, and the complaint was repeatedly attributed to the original diagnosis of peripheral neuropathy. After several visits during a two-month period, the patient went to the emergency department. His left lower leg was dusky in color with extreme tenderness to palpation and his pulses could not be palpated. A computed tomography angiogram revealed complete occlusion of the left superficial femoral artery secondary to atherosclerotic peripheral arterial disease, which required emergent bypass surgery. Because of ischemia of his leg, he developed several infections postoperatively and ultimately required an above-the-knee amputation. Vascular surgeons believed the patient’s chronic burning pain was because of progressive peripheral arterial disease and not peripheral neuropathy.
DISCUSSION In this case, despite repeated encounters with health care providers, the patient’s severe peripheral arterial disease was misdiagnosed, resulting in a serious adverse event. The case demonstrates errors because of diagnostic reasoning. Diagnostic errors are common. For every 1,000 primary care visits, there are approximately 20 diagnostic errors, from which one patient will seek unplanned medical help within two weeks.1 Approximately 27,000 hospital admissions per year in the United States are because of missed or delayed diagnoses in the ambulatory care setting,2 and 150,000 or more patients experience diagnosis-related harm on an annual basis.3 Also,
adverse events related to misdiagnosis are more likely to be judged preventable (ie, 80% of cases) than other types of adverse events such as medication errors (ie, 25% to 50% of cases).4 Approximately 75% of diagnostic errors have a cognitive component.5 Two cognitive components are the tendency to seek only as much information as necessary for an initial clinical impression and the tendency to stick with the initial impression even if new information becomes available. Premature closure is the failure to consider alternative diagnoses after the initial impression is formed. In this case, the first diagnostic misstep was failure to include peripheral arterial insufficiency in the initial diagnostic impression. In patients with foot pain, 15% have peripheral arterial insufficiency, so this diagnosis should be considered in every patient with this clinical presentation.6 Premature closure is exacerbated by anchoring, the tendency for clinicians to stick with the initial impression even as new information becomes available. This patient presented six times during two months with worsening symptoms, yet the diagnostic impression did not change and the management plan was simply repeated. Progressive severe unilateral foot pain should have launched an exploration of other possibilities because most neuropathy pain is bilateral. continued on page 631 This content is adapted from AHRQ WebM&M (Morbidity & Mortality Rounds on the Web) with permission from the Agency for Healthcare Research and Quality. The original commentary was written by Edward Etchells, MD, MSc, and was adapted for this article by Nancy J. Girard, PhD, RN, FAAN, consultant/owner, Nurse Collaborations, Boerne, TX. (Citation: Etchells E. Anchoring bias with critical implications. AHRQ WebM&M [serial online]. http:// webmm.ahrq.gov/case.aspx?caseID¼350. Published June 2015. Accessed February 22, 2016.) Dr Girard has no declared affiliation that could be perceived as posing a potential conflict of interest in the publication of this article. http://dx.doi.org/10.1016/j.aorn.2016.03.012 ª AORN, Inc, 2016
658 j AORN Journal
www.aornjournal.org
June 2016, Vol. 103, No. 6
continued from page 658 A number of cognitive biases contribute to anchoring. The first is confirmation bias, the tendency to selectively seek information that supports initial impressions. Confirmation bias can be reduced by being receptive to new information, such as from the history or physical examination, which could lead to an alternate diagnosis. A second bias is the tendency to overvalue irrelevant information. A third bias, anchoring bias, is inadequate adjustment of probabilities as new disconfirming information becomes available.7 Fourth, clinicians tend to stick with initial impressions as the number of new possible alternative diagnoses increases, referred to as status quo bias. Finally, framing effects can significantly influence diagnostic thinking when forming or revising diagnostic impressions. The framing effect is the tendency to be affected by how information is presented. Framing difficult cases without diagnostic labels and with appropriate uncertainty could reduce anchoring. Despite some limitations in research data, several cognitive- and system-based interventions hold promise for helping to prevent diagnostic errors, such as cognitive awareness. Awareness of cognitive biases and their contribution to diagnostic errors might help clinicians avoid such errors. Improving cognitive awareness could begin with efforts to teach trainees and practicing clinicians about the diagnostic thinking process and could continue through teamwork and case discussions. System-based tools might have improved the results of this case. Structured diagnostic assessments can be augmented by systems that provide guidance about a particular clinical decision at the point of care. For example, such decision support systems could ensure that symptoms of disease are considered and the specificity of common diagnostic tests is available.8 In this case, decision support might have helped the clinician identify arterial disease as a consideration or displayed the evidence to ensure the correct interpretation of the peripheral arterial examination. Computer-assisted diagnostic expert systems are designed to help avoid diagnostic errors.9 For this case, a computer-assisted diagnosis program was provided with the terms “pain left foot, numbness left foot, foot drop, loss of sensation left leg.” The program offered five diagnostic possibilities, including thromboangiitis obliterans, which might have prompted the clinician to consider vascular causes of the patient’s symptoms.
www.aornjournal.org
Perioperative Grand Rounds
In this case, several providers succumbed to common cognitive biases that led to premature closure as well as anchoring on the diagnosis of peripheral neuropathy. More formal education, case conferences, real-time decision support, or application of a computerized diagnostic aid might have prevented this error and the subsequent adverse event.
PERIOPERATIVE POINTS Anchoring is the tendency to stick with initial impressions even as new information becomes available, and this tendency can pose clinical risks. Anchoring could be reduced if clinicians o actively seek information that could refute the current provisional diagnosis; o avoid premature diagnostic labeling and share uncertainty; and o use system-based interventions such as structured diagnostic assessments, diagnostic decision support, and computerized expert diagnostic systems.
References 1. Singh H, Giardina TD, Meyer AN, Forjuoh SN, Reis MD, Thomas EJ. Types and origins of diagnostic errors in primary care settings. JAMA Intern Med. 2013;173(6):418-425. 2. Woods DM, Thomas EJ, Holl JL, Weiss KB, Brennan TA. Ambulatory care adverse events and preventable adverse events leading to a hospital admission. Qual Saf Health Care. 2007; 16(2):127-131. 3. Newman-Toker DE, Makary MA. Measuring diagnostic errors in primary care: the first step on a path forward. Comment on “Types and origins of diagnostic errors in primary care settings.” JAMA Intern Med. 2013;173(6):425-426. 4. Leape LL, Brennan TA, Laird N, et al. The nature of adverse events in hospitalized patients. Results of the Harvard Medical Practice Study II. N Engl J Med. 1991;324(6):377-384. 5. Schiff GD, Hasan O, Kim S, et al. Diagnostic error in medicine: analysis of 583 physician-reported errors. Arch Intern Med. 2009; 169(20):1881-1887. 6. Dunn JE, Link CL, Felson DT, Crincoli MG, Keysor JJ, McKinlay JB. Prevalence of foot and ankle conditions in a multiethnic community sample of older adults. Am J Epidemiol. 2004;159(5):491-498. 7. Tversky A, Kahneman D. Judgment under uncertainty: heuristics and biases. Science. 1974;185(4157):1124-1131. 8. McDonald KM, Matesic B, Contopoulos-Ioannidis DG, et al. Patient safety strategies targeted at diagnostic errors: a systematic review. Ann Intern Med. 2013;158(5 pt 2):381-389. 9. Graber ML, Mathew A. Performance of a web-based clinical diagnosis support system for internists. J Gen Intern Med. 2008; 23(suppl 1):37-40.
AORN Journal j 631