AUSTIN – Lack of upper motor neuron signs on examination, presence of sensory symptoms, and absence of tongue fasciculations are common causes of amyotrophic lateral sclerosis (ALS) misdiagnosis, according to an investigation presented at the annual meeting of the American Association of Neuromuscular and Electrodiagnostic Medicine.

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Because its initial presenting symptoms vary, ALS can be difficult for clinicians to diagnose. A diagnostic error may prompt clinicians and patients to pursue ineffective and potentially harmful medical or surgical interventions. Research suggests that surgery, for example, hastens the progression of ALS.

Catherine Rodriguez, a medical student at University of Missouri in Columbia, and colleagues conducted a study to identify the clinical factors and types of cognitive errors that can result in misdiagnosis of ALS. The researchers analyzed electronic medical records of 88 patients with a diagnosis of ALS who were receiving treatment at the University of Missouri Hospital during 2011-2017 with at least 1 year of follow-up. They collected demographic information and clinical characteristics (e.g., ALS Functional Rating Scale and site of symptom onset) for each patient. If a patient received an incorrect diagnosis, Ms. Rodriguez and colleagues recorded the number of physicians he or she had seen, the incorrect diagnosis, the treatment, the type of diagnostic error, the clinical factors contributing to the misdiagnosis, and the type of physician who gave the incorrect diagnosis.

The investigators classed diagnostic errors according to the four categories of cognitive bias of the Patient Safety Network. The categories are availability heuristic (i.e., the diagnosis of a current patient is biased by the clinician’s experience with previous cases), anchoring heuristic (i.e., relying on the initial impression despite the emergence of evidence that may contradict it), framing effects (i.e., subtle cues and collateral information bias the diagnosis), and blind obedience (i.e., undue reliance on test results or expert opinion). Ms. Rodriguez and colleagues used Fisher’s exact test to perform a statistical analysis of the data.

Thirty-four (39%) of the 88 patients were female, and the populations average age was about 60 years. Eighty patients (91%) were white, six (7%) were black, and two (2%) were Hispanic. Twenty patients (23%) received an incorrect diagnosis. Common incorrect diagnoses included spinal abnormality, Bell’s palsy, myasthenia gravis, ulnar neuropathy, autoimmune motor neuropathy, and stroke.

The investigators observed significant differences in the reasons for misdiagnosis, depending on patient characteristics. Veterans were misdiagnosed because of the availability heuristic, while nonveterans were misdiagnosed because of the anchoring heuristic. Lower-limb onset was most commonly misdiagnosed because of the anchoring heuristic. Bulbar onset was most commonly misdiagnosed because of the availability heuristic. Surgical intervention was the most common treatment for an incorrect diagnosis.

The data serve as a reminder of the prevalence of cognitive biases, said Ms. Rodriguez. “Common things are common, so we tend to stick with those [diagnoses]. Especially with ALS, nobody wants to give anyone that diagnosis.” Clinicians should “recognize that incorrect diagnoses have equally bad outcomes for those patients,” she concluded.

The study was supported by a University of Missouri School of Medicine Summer Research Fellowship Program.

egreb@mdedge.com

SOURCE: Rodriguez C et al. AANEM 2019. Abstract 10. Diagnostic errors and the implications for amyotrophic lateral sclerosis patients.

Researchers identify common reasons for misdiagnosis of ALS