The diagnosis of diseases causing memory difficulties or dementia is often challenging. Without the use of advanced methods such as cerebrospinal fluid tests, approximately 25-30% do not receive a correct diagnosis today. However, the investigators have recently developed new blood biomarkers with high diagnostic accuracy, and the investigators now want to investigate whether they can eventually replace cerebrospinal fluid tests. This is because blood tests are much more cost-effective and significantly easier for patients compared to cerebrospinal fluid tests. In this study, 1200 patients undergoing clinical evaluations at the Memory Clinic, Skåne University Hospital in Malmö, are included for blood and cerebrospinal fluid sample collection. The blood samples are sent for analysis using the new blood biomarkers. Subsequently, the results are compared with those from the clinical analysis of cerebrospinal fluid to determine how well they perform in routine clinical practice as an alternative to cerebrospinal fluid tests and whether the blood test improves patient care. This comparison is carried out by the attending physician in three steps: 1. Assessment without access to the results of either the blood test or cerebrospinal fluid test. 2. Assessment with access to only the results of the blood test. 3. Assessment with access to the results of both the blood test and cerebrospinal fluid test. Aim 1) To prospectively validate plasma Alzheimer's disease (AD) biomarkers for diagnosis of patients with cognitive symptoms who are evaluated in a specialist memory clinic. Aim 2) Determine whether blood AD biomarkers improve patient management in specialist memory clinic settings.