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Data File FAQ

Frequently Asked Questions about Data Files and the UDS

My data download link has expired - can you send me a new one?

  • Download links expire after two weeks. If you need to download data after this time, please send an email to consnacc@uw.edu with your data request # to request an updated link.

Does my collaborator need to sign the data use agreement (DUA)? I have new collaborators / I'm no longer working with a collaborator. What do I need to do regarding the DUA?

  • All collaborators are bound by the terms of the data use agreement, so you can freely share the data with collaborators on your analysis. You do not need to notify NACC of changes in your collaborators. If your collaborator is preparing the manuscript for this analysis, they should refer to the Checklist for Authors on the Publish with NACC Data page. If you wish to share the data with someone who will not be directly collaborating on your analysis, they will need to submit a new data request and separately sign the DUA.

How can I get an update to a data file from a previous request?

  • Please submit a new data request and indicate that you are requesting an update, with the data request # or file name of the previous request.

Can you provide a sample size estimate for my analysis before I request data?

  • NACC no longer provides sample size estimates for investigators. You can use the Query System to explore the sample size for simple criteria. You can also request the Quick-Access dataset through the Data Request System to explore the dataset in more detail.

Why does my proposal and/or publication not appear on the Ongoing & Completed Research page on NACC's website?

  • This page is currently under construction. Please check back later.

How was a variable (e.g. Alzheimer's disease clinical diagnosis) defined?

  • In addition to the Researcher's Data Dictionaries (RDDs), please refer to the data collection forms and coding guidebooks for each dataset for more information on variable definitions. In particular, the coding guidebooks provide detailed, annotated explanations of each form on an item-level basis, with instructions, operational definitions, and references. See the Forms page for RDDs, forms, and coding guidebooks for the following:
    • UDSv3, UDSv2, UDSv1.2
    • FTLD Module v3, FTLD Module v2
    • LBD Module v3.1 (short version), LBD Module v3
    • Down Syndrome Module
    • NPv11, NPv10, NPv9, NPv1-8
    • Imaging, CSF, and Genetic data

Do I need to submit my dissertation for administrative review?

  • You only need to submit manuscripts for review before they are submitted to a journal. Please only submit any part of your thesis that is prepared for manuscript submission.

I need a specific imaging type for my study. What does NACC's imaging database include?

  • MRI, amyloid PET, and tau PET scans and data are available on a subset of UDS participants via data request. NACC data includes MRI and PET variables associated with DICOM files stored at NACC and Standardized Centralized Alzheimer’s Disease and Related Dementias Neuroimaging (SCAN), as well as a database of Mixed Protocol (formerly ‘Legacy’) MRI and PET images.
  • Other imaging information:
    • Please note that for Mixed Protocol MRIs we are unable to separate packages of MRI files into sequence types.
    • For an estimate of the number of available Mixed Protocol scans that meet your image-type and subject criteria, use NACC’s MRI Preview System.
    • Some examples of data that are not available: functional MRI (fMRI), Magnetic Resonance Spectroscopy (MRS), Arterial spin labeling (ASL), and FDG PET.

How are SCAN and Mixed Protocol imaging data structured?

  • MRI, amyloid PET, and tau PET scans and data are available on a subset of UDS participants. NACC data includes MRI and PET variables (e.g., year of MRI scan, year of amyloid PET scan) associated with DICOM files stored at SCAN. NACC also maintains a database of heterogenous (formerly ‘Legacy’) MRI and PET images.
  • SCAN: Standardized Centralized Alzheimer’s Disease and Related Dementias Neuroimaging
    • The goal of SCAN is to enable standardized PET and MRI data collection from across the ADRC Program. The imaging data available on a subset of UDS participants includes MRI and PET variables (e.g., year of MRI scan, year of amyloid PET scan) associated with DICOM files collected by SCAN.
    • For a subset of MRI and PETs, defaced image data and calculated summary data are also available. This summary data includes volumetric, cortical thickness, and surface area analysis data for SCAN MRI and Standardized Uptake Value Ratio (SUVR) analysis data for SCAN PET.
  • Mixed Protocol MRI and PET
    • Mixed Protocol imaging data collection and acquisition protocols vary by ADRC. Packages of MRI files at NACC may include T1-weighted, FLAIR, DTI, T2, or other MR series (and any combination thereof). Only amyloid PET scans are available in the Mixed Protocol PET files at NACC. Subjects may or may not have multiple scan sessions in the NACC database.
    • For a subset of the MRIs, calculated summary data are also available. Included are MRI variables that provide volume values (e.g., hippocampal volume) and cortical thicknesses for the subset of DICOM files stored at NACC for which analysis has been completed. The calculations were performed by then IDeA Lab (Director: Charles DeCarli, MD; University of California, Davis), following ADNI protocols. For specific methods used to perform these calculations, please see IDeA Lab publications.
    • For an estimate of the number of available Mixed Protocol MRIs that meet your image-type and subject criteria, use NACC’s MRI Preview System.
    • To acquire images and volume data, submit a data request. Both DICOM and NIfTI formats are available. Images archived by subject ID and date (.zip), delivered via a cloud-based distribution system and linked to any requested UDS, FTLD, or NP data.
    • Image acquisition period2005 – present
      SubjectsADRC subjects enrolled in the Uniform Data Set (UDS)
      Clinical diagnosesNormal cognition, MCI, dementia
      Linked genotype dataAvailable from ADGC and NIAGADS
      Longitudinal MRIsAvailable for some subjects

Can you provide the predefined cutoff values for CSF biomarkers, or the assays used at each Center?

  • The CSF biomarker values can vary by assay method (ELISA, Luminex, etc.) and Center. Centers use different lab assay kits which provide ranges for amyloid beta and tau that are scaled completely differently for each brand of kit and have different range and cut off values for positivity. Unfortunately, we do not currently have information on the assay kits used or the cutoff values, so we strongly caution using the data for analysis.

I would like to use NACC's forms in my research study outside of the ADRC program. How can I obtain permission for this?

There are some variables missing from my Quick Access File. Where can I find them?

  • All of the variables in the Researchers Data Dictionary (RDD) (excluding CLS, and Z1X) are included in the Quick Access Files.

I want to determine if NACC UDS participants overlap with the ADNI cohort, DIAN study, or NIFD/FTLDNI. Can you provide me with participants lists that overlap?

  • No, we do not have information about overlapping participants in these studies.

When/how should the COVID forms be collected?

  • The collection of the current COVID Impact Survey (Forms F2/F3) is up to the discretion of the ADRCs, because it is not tied to a UDS visit. That said, we encourage you to collect this information at least annually.

I am part of an ADRC Neuropathology Core and was given a list of NACCIDs from a NACC tissue request. How do I map to PTID?

  • Log into the UDS submission system (or log in to the ADRC Portal and click “Submit UDS, FTLD, & LBD”). Under “DOWNLOAD DATA,” select the last link, “PTID to NACCID Map.”