The diagnostic value of plasma phosphorylated tau 181 in AD within the Chinese population: A systematic review and meta-analysis

Among all related biomarkers, plasma phosphorylated tau (p-tau181) has demonstrated strong diagnostic performance in the very early stages of Alzheimers disease (AD), showing significant differences between AD patients and healthy controls. The aim of our present systematic review and meta-analysis was to roundly evaluate the clinical diagnostic value of plasma p-tau181 based on the Simoa platform in Chinese populations. We systematically searched five databases (Embase, PubMed, Cochrane Library, MEDLINE, and Web of Science) from inception to May 11th, 2024, as well as the references of retrieved relevant articles. We included prospective cohort studies and retrospective case-control studies in our analysis. Out of 1165 identified articles, 10 met the inclusion criteria for meta-analysis. Our quantitative analysis showed that plasma p-tau181 levels were significantly increased in patients with AD and mild cognitive impairment (MCI) compared to healthy controls (standard mean difference [SMD]: 1.45 [1.25 - 1.65], p<0.00001; SMD: 0.55 [0.31 - 0.78], p<0.00001) and were lower in MCI patients compared to AD patients (SMD: -0.88 [-0.93 - -0.82], p<0.00001). The reference values for plasma p-tau181 were 4.48 [95% confidence interval (CI): 4.01 - 5.00] for AD patients, 2.86 [95% CI: 2.45 - 3.34] for MCI patients, and 2.09 [95% CI: 1.90 - 2.30] for healthy controls. The meta-analysis confirmed that plasma p-tau181 significantly increases from healthy controls to mild cognitive impairment (MCI) and then to AD in the Chinese population. We also provide reliable reference values for plasma p-tau181, which contribute to the early diagnosis of AD in Chinese clinical settings.