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Question Posted 01/12/24:
Dear ADNI Experts,

Could you please explain the difference between 'Research Group' in the advanced search results and 'DX_bl' in the ADNIMERGE csv file? I assumed they were the same, but after a quick investigation I found that they differ in some cases. For example, one patient is labelled CN in ADNIMERGE but AD in the advanced search results.

Thank you very much in advance!
Response posted 01/12/24 by Danielle:
In general, Research Group in the IDA refers to the screening diagnosis (in the ARM table for ADNI-1/GO/2; Diagnosis in the Diagnostic Summary file for the screening visit). There may be some instances where this doesn't quite match, which could be due to updates made to the data from the site, which would not change the Research Group designation in the IDA. The Clinical Core generally recommends using the diagnosis at the baseline visit (not screening visit) as the initial diagnosis, since this diagnosis is based on the full information rather than just what is collected at screening. The screening diagnosis, especially in earlier phases of ADNI, determined the visitation schedule.
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