Study of the utility and impact of a plasma p-tau181 Alzheimer's biomarker (SUITABLE).

INTRODUCTION

Blood-based Alzheimer's disease (AD) biomarkers are increasingly used in clinical care, but there are few real-world studies of their clinical utility. We evaluated the impact of plasma phosphorylated tau at threonine 181 (p-tau181) on the diagnosis and management of patients with cognitive impairment in a memory clinic.

METHODS

Dementia specialists referred patients for plasma p-tau181 testing during clinical care. We used surveys and chart review to assess the impact of plasma p-tau181 testing on clinical care and patient and care partner wellbeing. We assessed co-primary outcomes of (1) change in diagnostic confidence before vs after testing, (2) change in diagnosis, and (3) change in management. A diagnosis or management change of greater than 30% was considered to be clinically significant. Secondary and exploratory outcomes included impact of plasma p-tau181 testing on the use of additional diagnostics and impact on patient and care partner psychological wellbeing, health behaviors, and future planning.

RESULTS

One hundred patients completed plasma p-tau181 testing; 81% had an elevated result, and 19% had a non-elevated result. Clinician diagnostic confidence averaged 1.43 points higher after p-tau181 testing (95% confidence interval [CI] 1.02 to 1.84, p < 0.0001). After testing, 27.7% (95% CI 18.9% to 36.4%, p = 0.31) of patients had a change in management and 17.2% of patients had a change in diagnosis - significantly lower than the 30% threshold (95% CI 9.5% to 24.9%, p = 0.004). Patients with elevated results were less likely to have a diagnosis changed after testing than those with non-elevated results (OR 0.08 [95% CI 0.01 to 0.47], p = 0.005). A non-elevated result was associated with decreased use of amyloid positron emission tomography (PET) (odds ratio [OR] 0.25 [95% CI 0.07 to 0.86], p = 0.028). Patients with an elevated result had higher anxiety at 2 to 3 months after disclosure (p = 0.01).

DISCUSSION: Non-elevated plasma p-tau181 results impacted the diagnosis and use of amyloid PET imaging in a memory clinic. There was increased anxiety in patients after testing, affirming the need for post-disclosure psychological support.