[Role of the Aß1-42/Aß1-40 ratio in the concept 'Alzheimer's disease contributes to mild cognitive impairment'].

Introduction: Evidence of cerebral amyloidosis, by altered levels of the peptide Aß1-42 or the Aß1-42/Aß1-40 ratio, is a necessary condition to accept the presence of Alzheimer's disease (AD), according to the 2018 criteria of the National Institute on Aging and Alzheimer's Association (NIA-AA 2018).

Aim: To calculate the diagnostic gain obtained from calculating the Aß1-42/Aß1-40 ratio with respect to the exclusive use of the peptide Aß42 to identify patients belonging to the 'Alzheimer's disease contributes to mild cognitive impairment (MCI)' group, according to NIA-AA 2018 criteria.

Patients And Methods: Between April 2018 and April 2020, we included 62 patients with MCI, according to Petersen's 2006 criteria, who underwent lumbar puncture as part of the diagnostic process.