What is it about?
A review about current progress towards the development of a blood test that could be used to identify individuals with Alzheimer's disease or who are in the early stages of the disease. We review the literature on a wide range of molecules whose concentration in blood has been suggested to be predictive of Alzheimer's disease, from genetics to proteins and small molecules. We highlight the current problems with these approaches, and how studies can be improved to increase the chance of a effective blood test being developed. At the same time we make clear that there is insufficient evidence that any currently proposed blood test would be useful either in the clinic or for selecting individuals for clinical trials.
Why is it important?
This review is important as it goes beyond the hype, pointing out the lack of replication of several studies that made major international news headlines. It is important as well because it offers some recommendations about how we can do better, including more transparent reporting of findings and greater statistical rigour. Most importantly, negative findings and negative replications need to be published so we can focus on the candidate markers most likely to lead to an effective test, if indeed it is possible to find one.