Impact of blood p-tau217 testing on diagnosis and diagnostic confidence in cognitive disorders: a real-world clinical study.

BACKGROUND: The blood biomarker p-tau217 has demonstrated high accuracy in predicting underlying Alzheimer's disease (AD) pathology. However, its feasibility and impact on clinician confidence and diagnosis in real-world clinical settings remain underexplored. We aimed to evaluate the effect of implementing blood p-tau217 testing on both diagnosis and diagnostic confidence in patients with cognitive symptoms across two different clinical settings: general neurology consultations referred from primary care and a specialized memory unit. METHODS: We included 200 consecutive new patients (38.5% with subjective cognitive complaints, 47.5% mild cognitive impairment, and 14% with dementia) evaluated for cognitive symptoms in two distinct clinical settings: general neurology and a memory unit. Attending neurologists were asked to record a pre-biomarker clinical diagnosis and their diagnostic confidence on a scale from 0 to 10. They repeated this assessment after receiving the p-tau217 results. RESULTS: Across the whole sample, 51/200 patients (25.5%) had a change in their diagnostic category after receiving p-tau217 levels. Furthermore, diagnostic confidence significantly improved from 6.90 ± 1.74 at the first visit to 8.49 ± 1.68 after the test. Changes in diagnosis and confidence were observed in both general neurology and memory unit settings, and across all clinical stages (subjective cognitive complaints, mild cognitive impairment, and dementia). Compared with the final diagnosis, the pre-biomarker diagnosis was maintained in 71/200 cases (75.5%) (Kappa = 0.576), while the post-biomarker diagnosis was maintained in 189/200 cases (94.5%) (Kappa = 0.906). CONCLUSIONS: Implementing p-tau217 in real-world clinical practice has a strong clinical impact, substantially improving diagnostic accuracy and confidence in both general neurology and memory units across all stages of cognitive decline.