De-duplication: Duplicates will be identified using both electronic files and manually,
both within and between case sources, using the name or initials, gender, date of birth,
ethnicity, zip code, or other available information, in keeping with HIPAA requirements
to use the least amount of PHI in conducting research. The number of duplicates
identified will be used to estimate completeness of ascertainment with the capture-
recapture method among the geographic centers.
Systematic re-ascertainment: A systematic case re-ascertainment process will be
conducted in 2012 for cases incident in 2006-2010 and in 2014 for 2008-2012 cohorts.
The purpose of re-ascertainment is to assure as complete ascertainment of diabetes cases
as possible, especially those with T2D, who, due to different care patterns, we theorize
are more likely to be missed by the SEARCH network prior to the close of the
registration window. Additional cases will be registered with the center and the CoC
with a flag to indicate that they were registered outside of the standard window.
Case Registration: Cases that are valid, eligible and unique will be registered by the
center with information being uploaded to the CoC. Minimal information about the
participant (age, gender, race/ethnicity, type of diabetes reported by clinician, center, date
of diagnosis, zip code or county of residence, and birth date) will be uploaded to the CoC
website in order to protect confidentiality. Names and addresses are not provided to the
CoC. In cases where duplicates and cases that are not valid or eligible are identified at a
later date, they will be unregistered by both the local center and the CoC.
Collection of Core Variables: A minimum amount of demographic and clinical
information is needed for all registered cases in order for the study to be able to provide
population-based rates of diabetes mellitus by age, gender, diabetes type and
race/ethnicity for the entire population of cases. This information is also critical in
assessing possible response bias to the in person research visit. This information is called
“core” information. The main sources of core data are medical records and the initial