Question on merging ADNIMERGE and dMRI tables

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Mahta Abbaspour

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May 19, 2026, 2:57:57 PMMay 19
to Alzheimer's Disease Neuroimaging Initiative (ADNI) Data

Hi everyone,

I had a question about merging variables from ADNIMERGE and the diffusion MRI (dMRI) tables. Specifically, I’m trying to link baseline diagnosis (DX) from ADNIMERGE to DTI scan sessions.

In the DTI table, there doesn’t seem to be a “bl” session, only “sc” and follow-up visits (yr1, yr2, yr3, etc.). When I merged these two, I noticed that for a handful of participants, the baseline diagnosis happend several months (>6 months) after the dMRI scan. For example:

  • sc dMRI scan: 7/17/17

  • bl diagnosis: 3/20/18 (8 months after the scan)

  • y4 follow-up: 5/20/22 (4 years after the scan)

Interestingly, for a very few participants in my cohort, the baseline diagnosis actually occurs before the dMRI scan.

Given these inconsistencies, I wanted to ask whether it is still appropriate to merge the “sc” DTI session with baseline diagnosis from ADNIMERGE. Although majority of participants have a short gap between their sc and bl diagnosis, given these observations, I wanted to ask this quetsion.

Thanks very much for your help!

Danielle J Harvey

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May 19, 2026, 3:02:23 PMMay 19
to adni...@googlegroups.com

Hi Mahta,

 

The initial visits for ADNI are split in 2: a screening visit and a baseline visit. These are often several weeks to months apart, and assessments/imaging done at screening is not repeated at baseline. MRI is part of the screening visit, but the “best” diagnosis is from the baseline visit. You can merge information from baseline visits to that from screening visits – depending on the information, you may want to retain the dates of screening and baseline, in case it is needed to give insight into time between information.

 

Danielle

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Mahta Abbaspour

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May 22, 2026, 10:06:57 AMMay 22
to adni...@googlegroups.com
That makes sense! Thank you. 

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