Using a composite index of socioeconomic status to investigate health disparities while protecting the confidentiality of cancer registry data

The lack of individual socioeconomic status (SES) information in cancer registry data necessitates the use of area-based measures to investigate health disparities. Concerns about confidentiality, however, prohibit publishing patients' residential locations at the subcounty level. We developed a census tract-based composite SES index to be released in place of individual census tracts to minimize the risk of disclosure. Two SES indices based on the measures identified in the literature were constructed using factor analysis. The analyses were repeated using the data from the 2000 decennial census and 2005-2009 American Community Survey to create the indices at two time points, which were linked to 2000-2009 Surveillance, Epidemiology, and End Results registry data to estimate incidence and survival rates. The two indices performed similarly in stratifying census tracts and detecting socioeconomic gradients in cancer incidence and survival. The gradient in the incidence is positive for breast and prostate, and negative for lung cancers, in all races, although the level varies. The positive gradient in survival is more salient for regional-staged breast, colorectal, and lung cancers. The census tract-based SES index provides a valuable tool for monitoring the disparities in cancer burdens while avoiding potential identity disclosure. This index, divided into tertiles and quintiles, is now available to the researchers on request.