Blood tests for AD pathology may improve diagnostic accuracy, treatment in primary care

Key takeaways:

• Adults with cognitive complaints received usual care by primary care physicians and were tested for blood-based biomarkers.
• PCPs correctly identified AD in 54% of cases, while blood tests detected more than 75%.

Utilization of blood tests to detect Alzheimer’s pathology may boost diagnostic accuracy and treatment in a primary care setting, according to research presented at the Alzheimer’s Association International Conference.

“Due to the lack of accurate diagnostic tools, it is currently very difficult for primary care doctors to identify Alzheimer’s disease, even among patients with cognitive impairment,” Sebastian Palmqvist, MD, PhD, of the Clinical Memory Research Unit at Lund University in Sweden, said in a related release. “This too often leads to diagnostic uncertainty and inappropriate treatment.”

Palmqvist and colleagues sought to assess the diagnostic accuracy of plasma phospho-tau217/nonphospho-tau217 (p-tau217 ratio) and amyloid-beta42/40 ratio for AD compared with standard care by primary care physicians.

They conducted the BioFINDER-Primary Care study, recruiting 307 participants (mean age, 76 years; 48% women; 49% with AD pathology) with cognitive complaints from 25 primary care centers in Sweden. Following a course of standard care, which included CT or MRI, cognitive testing and clinical assessment, PCPs recorded the most likely underlying cause of disease and proposed a treatment plan. Participants also submitted blood samples to test for plasma biomarkers, which included p-tau217 ratio, amyloid-beta42/40 ratio and an algorithm combining both.

The primary outcome was AD pathology using cerebrospinal fluid amyloid-beta42/p-tau181 or a visual read of 18F-Flutemetamol PET.

According to results, 25% of participants had subjective cognitive decline, 47% mild cognitive impairment and 28% dementia.

Using AD pathology as the outcome, researchers reported areas under the curve of 0.8 (95% CI, 0.75-0.86) for amyloid-beta42/40 ratio, 0.91 (95% CI, 0.88-0.94) for p-tau217 ratio and 0.94 (95% CI, 0.92-0.97) for the algorithm.

Among 265 participants with available PCP questionnaires, physicians correctly classified AD in 54% of the cases, compared with 77% for amyloid-beta42/40 ratio, 85% for p-tau217 ratio and 87% for the algorithm.

On a scale of 1 to 10, with 10 being completely certain, researchers reported the mean certainty of PCP diagnosis of AD was 4.7 (5.1 in those with AD pathology who were correctly diagnosed as AD and 4.6 in missed cases).

Additionally, among the 87% of PCPs who followed treatment guidelines, 50% of true AD cases did not receive symptomatic treatment and 30% of non-AD cases incorrectly received symptomatic AD treatment.

“Blood tests for Alzheimer’s disease have great potential for improving diagnostic accuracy and proper treatment,” Palmqvist said in the release. “These tests may become even more important in the near future, as new drugs that slow down the disease in its early stages become more widely available.”

Reference:

• Simple finger prick test exemplifies advances in Alzheimer’s disease blood tests. https://aaic.alz.org/releases_2023/finger-prick-blood-test-alzheimers-disease.asp. Published July 19, 2023. Accessed July 19, 2023.