Application of plasma phosphorylated tau 217 in a memory clinic focusing on Chinese patients

Introduction: Plasma phosphorylated tau (P-tau) 217 has not been extensively studied in the Chinese population in a real-world memory clinic for detecting Alzheimer’s disease (AD). This study aimed to determine a local cut-off for plasma P-tau 217 in a Chinese population and apply it to a similar cohort of patients in our memory clinic, evaluating its impact on diagnostic outcomes in a real-world setting. Methods: Ninety-eight patients were offered measurement of plasma P-tau 217 using S-PLEX ® . The validation cohort, consisting of 48 patients who underwent amyloid positron emission tomography (PET), was used to determine the cut-offs for plasma P-tau 217 and posttest probabilities through receiver operating curve analysis. Unsupervised clustering analysis was also used to derive the cut-off. These cut-offs were applied to an application cohort ( n = 50) without amyloid PET to study the clinical impact. Results: The sensitivity and specificity of the test, using a single cut-off of plasma P-tau 217 >10.08 pg/mL, were 86.67% and 88.89%, respectively. Unsupervised clustering analysis generated a cut-off of >11.69 pg/mL. After applying the two determined cut-offs in the application cohort, 50% of patients clinically diagnosed with AD were reclassified as non-AD, while 16.7% of patients initially diagnosed as non-AD were reclassified as AD. Using a post-test probability cut-off of >39.41%, the classification of AD and non-AD patients had a sensitivity of 93.33% and a specificity of 88.89%. Conclusion: Plasma P-tau 217 is useful in diagnosing AD among Chinese patients in a memory clinic with diverse underlying aetiologies of cognitive impairment.