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Richard M. Schwartzstein, MD
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From the Division of Pulmonary and Critical Care Medicine, Department of Medicine, Beth Israel Deaconess Medical Center.

Correspondence to: Richard M. Schwartzstein, MD, Division of Pulmonary and Critical Care Medicine, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215; e-mail: rschwart@bidmc.harvard.edu


Financial/nonfinancial disclosures: The author has reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


© 2012 American College of Chest Physicians


Chest. 2012;141(6):1637. doi:10.1378/chest.12-0182
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To the Editor:

I thank Drs Aberegg and O’Brien for their letter regarding our recent article in CHEST.1 Their concerns focus on two issues that arose in our discussion of cognitive bias: the definitions of availability and anchoring bias and the failure to describe “inadequate search” as the primary cognitive mistake.

Tversky and Kahneman2 describe the availability bias as the assessment of a “probability of an event by the ease with which instances or occurrences can be brought to mind.” The resident in this case was convinced that the diagnosis of pulmonary embolism was correct because he had seen many cases of pulmonary embolism in the past, and these cases were associated with gas exchange abnormalities. The ease with which this diagnosis was brought to mind enhanced the probability (as judged by the resident) of it being correct. Croskerry3 defines availability bias as “the tendency for things to be judged more frequent if they come readily to mind”; I submit this is a fair representation of the original description.

I also describe the resident’s thinking as being affected by anchoring bias. Although the original description of anchoring derived from experiments with numbers, I believe my use of the term here is also an appropriate interpretation in a medical context: “anchoring is the tendency to fixate on specific features of a presentation too early in the diagnostic process.”3 The problem was not that the resident failed to notice that the patient had bilateral lower extremity amputations or a distended abdomen; rather, he had “fixated” on his original diagnosis and was unwilling to modify his thinking based on these data. Use of the term, anchoring, in this way is in the spirit of Kahneman,4 who writes, “the availability of a diagnostic label…makes it easier to anticipate, recognize and understand.” As a medical educator, I find that identification of this common cognitive error as “anchoring” facilitates teaching students and residents about decision making.

Finally, Drs Aberegg and O’Brien assert that the real problem was an inadequate search for other possibilities, an explanation that could be used for any and every erroneous diagnosis that was based on a list of possibilities, no matter how long, if it did not include the ultimate answer. More importantly, however, many questions in medicine do not lend themselves to an easy search of textbooks or the medical literature. Aberegg et al5 propose teaching medical students to use Internet searches based on the chief complaint to ensure an adequate search has occurred. Following that strategy for “rising Paco2,” the resident’s description of the major problem in this case, I went through the first five pages of Internet hits and found no references that would give you the correct answer for this case, other than those that cite the article that is the topic of this discussion.1 I agree that we must slow down and use system II reasoning. But it is my contention, and the focus of the Interactive Physiology Grand Rounds series,6 that reasoning based on an analysis of a problem using basic principles of physiology and pathophysiology can lead one to an accurate diagnosis in these more complex cases.

Schwartzstein RM, Parker MJ. Rising Paco2in the ICU: using a physiologic approach to avoid cognitive biases. Chest. 2011;1406:1638-1642. [CrossRef] [PubMed]
 
Tversky A, Kahneman D. Judgment under uncertainty: heuristics and biases. Science. 1974;1854157:1124-1131. [CrossRef] [PubMed]
 
Croskerry P. Achieving quality in clinical decision making: cognitive strategies and detection of bias. Acad Emerg Med. 2002;911:1184-1204. [CrossRef] [PubMed]
 
Kahneman D. Thinking Fast and Slow. 2011; New York, NY Farrar, Strauss, and Giroux
 
Aberegg SK, O’Brien JM, Lucarelli M, Terry PB. The search-inference framework: a proposed strategy for novice clinical problem solving. Med Educ. 2008;424:389-395. [CrossRef] [PubMed]
 
Schwartzstein RM, Parker MJ. Interactive physiology grand rounds: introduction to the series. Chest. 2009;1351:6-8. [CrossRef] [PubMed]
 

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References

Schwartzstein RM, Parker MJ. Rising Paco2in the ICU: using a physiologic approach to avoid cognitive biases. Chest. 2011;1406:1638-1642. [CrossRef] [PubMed]
 
Tversky A, Kahneman D. Judgment under uncertainty: heuristics and biases. Science. 1974;1854157:1124-1131. [CrossRef] [PubMed]
 
Croskerry P. Achieving quality in clinical decision making: cognitive strategies and detection of bias. Acad Emerg Med. 2002;911:1184-1204. [CrossRef] [PubMed]
 
Kahneman D. Thinking Fast and Slow. 2011; New York, NY Farrar, Strauss, and Giroux
 
Aberegg SK, O’Brien JM, Lucarelli M, Terry PB. The search-inference framework: a proposed strategy for novice clinical problem solving. Med Educ. 2008;424:389-395. [CrossRef] [PubMed]
 
Schwartzstein RM, Parker MJ. Interactive physiology grand rounds: introduction to the series. Chest. 2009;1351:6-8. [CrossRef] [PubMed]
 
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