Pre-visit Diagnosis in baseline change file

[John]

Dear ADNI experts,

I am selecting ADNI subjects, but there are something unclear for me.

May I have your opinion on this subject?

I have used DXSUM, ADNIMERGE data to define diagnosis for each RID.
However, there are still NA in the diagnosis.
For example, some RID have diagnosis patterns like
CN NA NA NA CN CN
I am not sure whether I can treat those NA NA NA as CN.


Also, from the worksheet packet of ADNI1, I can read "DXCONTYP" or "DXREV"
variable can indicate changes of diagnosis, but I cannot find this column on the following files
- ADNIMERGE.csv
- DXSUM_PDXCONV.csv

So, I tried to use BLCHANGE.csv file which has no columns named "DXCONTYP" and "DXREV".
This file has a column named "BCPREDX".

So, here are my questions.
Q1) How can I fill the NA diagnosis? Should I refer to other files instead of ADINMERGE.csv  and DXSUM_PDXCONV.csv files?
Q2) Does "BCPREDX" column in BLCHANGE.csv file mean the diagnosis at the VISCODE?
 
  I really appreciate your dedication in advance.

Sincerely

John

[Danielle J Harvey]

Hi John,

 

There are many rows in ADNIMERGE that contain very little data (could be from an MRI only visit such as m03 or a telephone follow-up). Generally speaking, after m24, clinical visits (when a diagnosis is made) happen annually. Likely most of the rows with NA in the DX column in ADNIMERGE are from non-annual visits, when we do not expect to have a diagnosis (VISCODE is “m” followed by number of months, so unless that number is divisible by 12, you will not have a diagnosis.

 

Throughout ADNI, diagnosis has been captured through different variables (diagnosis in ADNIMERGE consolidated that information into a single variable: DX). In ADNI-4, we are making an effort to harmonize data across the phases of ADNI and the Diagnostic Summary file (DXSUM_PDXCONV) is one in which we have done that, so all of the phase-specific diagnostic variables have been removed. If you want to identify changes in diagnosis, you will need to do that yourself by looking at the sequence of diagnoses for an individual.

 

The Diagnostic Summary file  (DXSUM_PDXCONV) is the best place to find diagnosis.

 

Danielle

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