Diagnostic challenges in primary care: Identifying and avoiding cognitive bias

Medical errors in all settings contributed to as many as 250,000 deaths per year in the United States between 2000 and 2008, according to a 2016 study.¹ Diagnostic error, in particular, remains a leading cause of morbidity and mortality in the United States and worldwide. In 2017, 12 million patients (roughly 5% of all US adults) who sought outpatient care experienced missed, delayed, or incorrect diagnosis at least once.²

In his classic work, How Doctors Think, Jerome Groopman, MD, explored the diagnostic process with a focus on the role of cognitive bias in clinical decision-making. Groopman examined how physicians can become sidetracked in their thinking and “blinded” to potential alternative diagnoses.³ Medical error is not necessarily because of a deficiency in medical knowledge; rather, physicians become susceptible to medical error when defective and faulty reasoning distort their diagnostic ability.⁴

Cognitive bias in the diagnostic process has been extensively studied, and a full review is beyond the scope of this article.⁵ However, here we will examine pathways leading to diagnostic errors in the primary care setting, specifically the role of cognitive bias in the work-up of polymyalgia rheumatica (PMR), ovarian cancer (OC), Lewy body dementia (LBD), and fibromyalgia (FM). As these 4 disease states are seen with low-to-moderate frequency in primary care, cognitive bias can complicate accurate diagnosis. But first, a word about how to understand clinical reasoning.

There are 2 types of reasoning (and 1 is more prone to error)

Physician clinical reasoning can be divided into 2 different cognitive approaches.

Type 1 reasoning employs intuition and heuristics; this type is automatic, reflexive, and quick.⁵ While the use of mental shortcuts in type 1 increases the speed with which decisions are made, it also makes this form of reasoning more prone to error.

Type 2 reasoning requires conscious effort. It is goal directed and rigorous and therefore slower than type 1 reasoning. Extrapolated to the clinical context, clinicians transition from type 2 to type 1 reasoning as they gain experience and training throughout their careers and develop their own conscious and subconscious heuristics. Deviations from accurate decision-making occur in a systematic manner due to cognitive biases and result in medical error.⁶table 1⁷ lists common types of cognitive bias.

An important question to ask. Physicians tend to fall into a pattern of quick, type 1 reasoning. However, it’s important to strive to maintain a broad differential diagnosis and avoid premature closure of the diagnostic process. It’s critical that we consider alternative diagnoses (ie, consciously move from type 1 to type 2 thinking) and continue to ask ourselves, “What else?” while working through differential diagnoses. This can be a powerful debiasing technique.

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