Question

Question Posted 03/26/17:
Dear experts,

(1) I find some subjects in ADNI2 have two resting state fMRI scans in a single visit, for instance, 006_S_4192, and I would like to know the reasons behind.
(2) I know that some subjects may have a different diagnosis in screening and baseline visits. Do the screening and baseline visits take place in the same day?
(3) I use ADNIMERGE.csv to obtain the subjects' age and MMSE scores in the baseline visit. It seems that the variables with a '_bl' suffix are actually the screening measurements and the variables without are the truely baseline measurements? Is that right?

Many thanks!
Response posted 03/27/17 by Danielle:
I am not sure about the reason for two rs-fMRI for some participants at the same visit - you might want to direct that question specifically to the MRI Core.

As for the baseline and screening visits, they are different visits occurring on different days. Each visit has specific information being acquired (you can download the complete ADNI visit schedule at http://adni.loni.usc.edu/methods/documents/). For example, MMSE was done at the screening visit.

My understanding of the ADNIMERGE file is that information acquired at either the screening visit or the baseline visit (since nothing is done at both) is considered "baseline". Variables that have the suffix "_bl" will contain the information from the 1st visit that acquired that information (either baseline or screening). Variables without the suffix (for example, ADAS11, contain the data at each visit).