The Colombian Alzheimer's Prevention Initiative (API) Trial is a collaborative project involving the Neurosciences Group of Antioquia (GNA), Genentech/Roche, National Institute of Health, and the Banner Alzheimer's Institute, studying whether crenezumab can delay or prevent the clinical onset of Alzheimer's disease in asymptomatic carriers of the PSEN1 E280A mutation. With the goals of decreasing screen failures and optimizing participant compliance and adherence, GNA implemented a prescreening process. The prescreening process started with the generation of lists of probably eligible candidates between 30 and 60 years of age, who belong to the Colombian API Registry. Lists were created automatically by the SISNE2 system and filtered by the responsible analyst, who selected candidates in a 2:1 carrier/noncarrier ratio. The clinical history of each candidate was reviewed by a subinvestigator who evaluated health status and whether inclusion/exclusion (I/E) criteria were met. All eligible candidates were contacted by telephone and invited for group Informed Consent (IC) meetings in which the principal investigator explained the trial, possible adverse effects, and medical procedures performed at each visit. They were given the IC and the study brochure to review at home with their families. At the end of the meeting, candidates filled out prescreening questionnaires regarding current health status and confirming that I/E criteria were met. Candidates were contacted once by telephone to establish whether they wanted to participant in the trial. If they did, a screening visit was scheduled. Prescreening process was approved by a local Ethics Committee. The total prescreening failure rate was 48.15%; of those, 66.6% were not invited to IC meeting due to not meeting specific I/E criteria. The most frequent causes for prescreening failures were: 39.0% expected inability to comply with visit, 13.0% mild cognitive impairment, 12.6% not in good health, 7.3% learning difficulties or illiteracy, 8.6% substance dependence, 6.6% pregnancy or willing to have kids and 6.0% dementia. The primary reason for prescreening failure in asymptomatic individuals was expected inability to comply with the visit schedule of the trial due to work related issues, which was anticipated since people are in a productive stage of their lives.