Quantification of the amount of beta-secretase 1 in a sample, typicallly cerebrospinal fluid. Beta-secretase-1 is an aspartic-acid protease important in the formation of myelin sheaths in peripheral nerve cells, and is thought to have a role in Alzheimer's disease pathogenesis. The trait is Experimental Factor Ontology entry EFO_0009179 (beta-secretase 1 measurement). Also known as: ASP2, BACE1, aspartyl protease 2, beta-site APP cleaving enzyme 1, beta-site amyloid precursor protein cleaving enzyme 1, memapsin-2, membrane-associated aspartic protease 2.