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The chief difference between a primary prevention trial and a secondary prevention trial (SPT) in Alzheimer disease (AD) is related to the targeted group of participants. As currently conceptualized, a primary prevention trial recruits asymptomatic individuals from the general population, whereas an SPT recruits only asymptomatic (or preclinical) individuals who are biomarker-positive for AD.1 Recent examples of the latter include the AD kindred trial in Antioquia, Colombia, which recruits only participants who are PS1 E280A mutation carriers with a familial history of early-onset disease, and the Anti-Amyloid Treatment in Asymptomatic Alzheimer’s study (hereafter referred to as the A4 study), which targets adults 70 years of age or older with high amyloid levels in the brain as determined by a positron emission tomographic scan. The latter study is the subject of the article by Donohue et al,2 who seek to identify a primary end point for that SPT.
Kryscio RJ. Secondary Prevention Trials in Alzheimer DiseaseThe Challenge of Identifying a Meaningful End Point. JAMA Neurol. 2014;71(8):947-949. doi:10.1001/jamaneurol.2014.1120