“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 dementia and dementia with Lewy bodies,” Corinne Fischer, M.D., director of the Memory Disorders Clinic at St. Michael’s Hospital in Toronto and lead author of the study, said in a press release. “Consequently, clinicians are more reluctant to diagnose a patient with Alzheimer’s disease when they present with delusions or hallucinations.”
Misdiagnosis of AD has significant implications for clinical care because patients may not receive appropriate treatment, which can impact clinical outcomes. For example, treatment with existing cholinesterase inhibitors has shown some effectiveness in AD, but limited effectiveness in other forms of dementia, such as vascular dementia and frontotemporal dementia.
Fischer and colleagues examined 961 people using data from the National Alzheimer’s Coordinating Center (NACC) database, collected from 29 Alzheimer’s disease centers in the United States between 2005 and 2012. They included participants who had been clinically diagnosed with AD while they were alive, and those whose autopsies showed the signature physical signs of AD in their brains.
A total of 76% of the patients received a correct AD diagnosis, 11.9% had a false-negative diagnosis, and 12.1% had a false-positive diagnosis of AD, the authors reported. Patients with psychosis had a higher rate of false-negative diagnosis and a lower rate of false-positive diagnosis of AD compared with nonpsychotic patients.
The researchers noted that most patients in the NACC database have been examined by clinicians with particular expertise in dementia, and the diagnosis given was the last one before death. Thus, the rates of misdiagnosis in this study should be considered to represent the minimum, reached under very favorable conditions. “If you extrapolate that and apply it to the general population, the magnitude of the problem could be much greater,” they wrote.
For related information, see the Psychiatric News article “New Dementia Measures Address Disclosure of Diagnosis to Patients.”