What is the difference between screening, initial and baseline visits?

[Reihaneh Ahmadi]

Hi, 

I want to conduct a longitudinal assessment and need images from the baseline and one-year follow-ups. But I'm confused about the difference between screening, initial and baseline visits. Can I consider each of these visits as a baseline point for my study?

thanks!

Reihaneh

[Danielle J Harvey]

Hi Reihaneh,

 

In ADNI, there is a screening visit and a baseline visit. The screening visit obtains information relevant to inclusion/exclusion criteria, while the baseline visit does a more comprehensive assessment of those that are deemed eligible for the study. Measures obtained at screening are not redone at baseline (except diagnosis, but diagnosis at screening is based on incomplete information and therefore only used for the visitation schedule – the diagnosis at the baseline visit should be treated as the initial diagnosis). Typically, the screening and baseline visits are within a few months of one another, and so can be considered the same visit, if you want to use measures obtained at both screening and baseline. You may see “init” for some VISCODEs – this is generally used for an initial visit in a new phase of ADNI for someone who was initially enrolled in an earlier phase (so, for example, a participant originally enrolled as part of ADNI-2, might have “init” for the first visit in ADNI-3. In many of the files downloaded from LONI, you will see VISCODE2, which translates the tracking VISCODE to something more meaningful (m60, for example, for the year 5 visit).

 

Danielle

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