Geographic variation of racial/ethnic disparities in colorectal cancer testing among medicare enrollees

Background: The Medicare population has documented racial/ethnic disparities in colorectal cancer (CRC) screening, but it is unknown whether these disparities differ across geographic regions. Methods: Among Medicare enrollees within 8 US states, we ascertained up-to-date CRC screening on December 31, 2003 (fecal occult blood testing in the prior year or sigmoidoscopy or colonoscopy in the prior 5 years). Logistic regression models tested for regional variation in up-to-date status among white versus different nonwhite populations (blacks, Asian/Pacific Islanders [APIs], Hispanics). We estimated regression-adjusted region-specific prevalence of up-to-date status by race/ethnicity and compared adjusted white versus nonwhite up-to-date prevalence across regions by using generalized least squares regression. Results: White versus nonwhite up-to-date status varied significantly across regions for blacks (P =.01) and APIs (P <.001) but not Hispanics (P =.62). Whereas the white versus black differences in proportion up-to-date were greatest in Atlanta (Georgia), rural Georgia, and the San Francisco Bay Area of California (range, 10%-16% differences, blacks<whites); there were no significant white versus black differences in Connecticut, Seattle (Washington) or Iowa. Whereas APIs had significantly lower up-to-date prevalence than whites in Michigan and the California regions of San Francisco, Los Angeles, and San Jose (range, 4%-15% differences, APIs<whites), APIs in Hawaii had higher up-to-date status than whites (52% vs 38% P <.001). White versus Hispanic differences were substantial but homogeneous across regions (range, 8%-16% differences, Hispanics<whites). In contrast to nonwhites, there was little geographic variation in up-to-date status among whites. Conclusions: Significant geographic variation in up-to-date status among black and API Medicare enrollees is associated with heterogeneous racial/ethnic disparities for these groups across US regions.