QUALITY ASSURANCE AND THE NACC DATABASE

Electronic error and alert checks

The NACC database of UDS subjects is made up of three data sets:

• Uniform Data Set
• Neuropathology Data Set
• FTLD Module Data Set

All told, the NACC database comprises more than 1,400 variables, each with its own coding requirements and allowable ranges. To help ensure the quality of new data being entered into the NACC database, NACC sets electronic error and alert checks that require ADCs to correct or verify questionable values before the data are accepted.

ERROR CHECKS require that ADCs change the data value to something in the allowable range before the subject's visit packet can enter the current database and be used for research. Examples of UDS error checks:

• Range error check: A reported height of 125 inches falls outside the allowable range.
• Within-form error check: If stroke is reported on the Form A5 (Subject Health History), then stroke year (or 9999=unknown) must be supplied.
• Cross-form error check: If a diagnosis of dementia is indicated on Form D1 (Clinician Diagnosis), then on Form B9 (Clinician Judgment of Symptoms), the age of onset of cognitive decline must be supplied.
• Cross-visit error check: If chronic traumatic brain injury is indicated on Form A5 (Subject Health History) at the initial UDS visit, then chronic traumatic brain injury must be indicated on Form A5 in a follow-up visit.

ALERT CHECKS require that ADCs either correct or verify the data value before the subject's visit packet can enter the database. Examples of alert checks:

• Within-form alert check: A reported weight of 425 pounds falls outside the expected range.
• Cross-form alert check: If the judgment score on Form B5 (CDR) indicates at least mild impairment in judgment, and yet no cognitive symptoms related to judgment are reported on Form B9 (Clinician Judgment of Symptoms), then an alert is triggered.
• Cross-visit alert check: If dementia is reported at one visit on Form D1 (Clinician Diagnosis) but not reported at the next visit, then an alert is triggered. This is flagged as an alert and not an error because although very rare, this kind of reversion can occur.

Please contact us for more information about NACC’s QA/QC efforts.