NEFL and neurodegenerative disease: Changes in NFL levels can be used to track disease progression and treatment response,51 and in humans increased levels are observed in a variety of neurodegenerative diseases, including AD and motor neuron disease.51s61–63 Serial NFL sampling in individuals at risk of AD predicts brain atrophy rates, cognitive impairment and disease progression.52 As plasma NFL levels are highly correlated with CSF NFL, blood testing of NFL is informative.53s62–64