Alzheimer’s Disease Patients with Psychosis Misdiagnosed at Higher Rates than Previously Thought, Study Finds

Patients with Alzheimer’s disease who experience delusions and hallucinations are five times more likely to be misdiagnosed than Alzheimer’s patients without psychosis, new research from St. Michael’s Hospital in Toronto, Canada, found.

The study, “Determining the impact of psychosis on rates of false-positive and false-negative diagnosis in Alzheimer’s disease,” was published in the journal Alzheimer’s & Dementia: Translational Research & Clinical Interventions.

Researchers discovered that Alzheimer’s patients with psychosis were misdiagnosed with another form of dementia in 24% of all cases, compared to previous research that suggested a range of 12-23%. Of the 24% of cases, 12% were false positives and 12% were false negatives, the study showed.

Psychosis is a typical symptom of other dementia types, and researchers believe that many physicians might be unaware of its link to Alzheimer’s disease.

About 36% of Alzheimer’s patients are thought to have delusions and 18% have hallucinations. Delusions and hallucinations are the two most prominent symptoms of a psychosis.

“Psychosis can be a symptom of Alzheimer’s disease, but it is a defining clinical feature in other types of dementia, including Parkinson’s disease related dementia and dementia with Lewy bodies,” said Corinne Fischer, MD, director of St. Michael’s Memory Disorders Clinic and lead author of the study.

“Consequently, clinicians are more reluctant to diagnose a patient with Alzheimer’s disease when they present with delusions or hallucinations,” she added.

For the study, researchers examined data on 961 people in the National Alzheimer’s Coordinating Center database. The study’s patients were treated at Alzheimer’s disease centers in the United States between 2005 and 2012. Not all of them were alive at the time of diagnosis — some had been diagnosed when doctors detected the telltale amyloid aggregates in their brains during autopsies.

“An advantage of our study is that we used the final clinical diagnosis after years of follow-up, so the rate of misdiagnosis we described is the rate under ideal conditions,” said Winnie Qian, a master’s student in the Neuroscience Research Program at St. Michael’s and study co-author.

“This means that it should be considered a minimum. If you extrapolate that and apply it to the general population, the magnitude of the problem could be much greater,” Qian added.

Dementia with Lewy bodies, like Alzheimer’s, is linked to protein aggregates in the brain. The type of protein, however, is different. When future treatments for both diseases are developed they will likely differ, making a correct diagnosis crucial.

According to Fisher, the study also provides information about factors that contribute to erroneous diagnoses.

“Many dementia patients never receive a definitive clinical diagnosis while they’re alive, so the hope is that by understanding what factors can lead to a misdiagnosis, we can be more accurate and provide patients with the best possible care,” she said.

Earlier studies show that psychotic symptoms are linked to a more rapid disease course with a higher loss of functional abilities. They also pose a heavy burden on caregivers, who are already under significant stress.