Diagnostic challenges in primary care: Identifying and avoiding cognitive bias

The discussion of the following 4 disease states demonstrates how cognitive bias can lead to diagnostic error.

Case 1

An 82-year-old woman with a history of hypertension; wide-angle glaucoma; stage 2 chronic kidney disease; osteopenia; severe osteoarthritis (OA) affecting the hips, shoulders, and knees; insomnia; and depression is transferred to a new family medicine practice for evaluation. She has been taking nonsteroidal anti-­inflammatory drugs (NSAIDs) for chronic pain secondary to OA for 6 months, with no improvement in symptoms.

The patient is barely able to ambulate and appears to be in considerable pain. She is relying heavily on her walker and is assisted by her granddaughter. The primary care physician (PCP) obtains a detailed history that includes chronic shoulder and hip pain. Given that the patient has not responded to NSAID treatment over the previous 6 months, the PCP takes a moment to reconsider the diagnosis of OA and considers other options.

It’s critical that we consider alternative diagnoses and continue to ask ourselves, “What else?” while working through differential diagnoses.

In light of the high prevalence of PMR in older women, the physician pursues a more specific physical examination tailored to ferret out PMR. He had learned this diagnostic shortcut as a resident, remembered it, and adeptly applied it whenever circumstances warranted. He asks the patient to raise her arms above her head (goalpost sign). She is unable to perform this task and experiences severe bilateral shoulder pain on trial. The PCP then places the patient on the examining table and attempts to assist her in rolling toward him. The patient is also unable to perform this maneuver and experiences significant bilateral hip pain on trial.

Based primarily on the patient’s history and physical exam findings, the PCP makes a presumptive diagnosis of PMR vs OA vs combined PMR with OA, orders an erythrocyte sedimentation rate (ESR) and basic rheumatologic marker panel, and starts the patient on prednisone 10 mg/d. Lab work comes back and reveals mildly elevated ESR with all other findings within normal limits. Two weeks later, the patient returns for her follow-up visit, walking without a walker for the first time in years.

PMR can be mistaken for OA

PMR is the most common inflammatory rheumatic disease in older patients.⁸ It is a debilitating illness with simple, effective treatment but has devastating consequences if missed or left untreated.⁹ PMR typically manifests in patients older than age 50, with a peak incidence at 80 years of age. It is also far more common in women.¹⁰

Approximately 80% of patients with PMR initially present to their PCP, often posing a diagnostic challenge to many clinicians.¹¹ Due to overlap in symptoms, the condition is often misdiagnosed as OA, a more common condition seen by PCPs. Also, there are no specific diagnostic tests for PMR. An elevated ESR can help confirm the diagnosis, but one-third of patients with PMR have a normal ESR.¹² Therefore, the diagnostic conundrum the physician faces is OA vs rheumatoid arthritis (RA), PMR, or another condition.

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