Birth Prevalence of Sickle Cell Trait and Sickle Cell Disease in Shelby County, TN

Background: Accurate quantification of the regional burden of sickle cell disease (SCD) is vital to allocating health-related resources. Shelby County, TN, which includes the city of Memphis and the regional pediatric SCD treatment center at St. Jude Children's Research Hospital, is home to a large population of African Americans.

Procedure: We postulated that the regional birth prevalence of SCD in Shelby County, TN, would differ from national rates. Using data from 2002 to 2012, we estimated the birth prevalence of SCD and sickle cell trait (SCT) in Shelby County and evaluated the distribution of SCD cases by ZIP code of residence with geographic information systems (GIS).

Results: The prevalence of SCD in African Americans was 1/287 (95% confidence interval [CI]: 1/323, 1/256) live births, significantly higher than the nationally reported 1/350 -1/500. The prevalence of SCT in African Americans was 1/14.7 (95% CI: 1/15.0, 1/14.3) live births, significantly lower than the nationally reported 1/12. We found that 48% of the SCD cases resided in only six of the 37 residential ZIP codes, and using GIS mapping there were two clusters composed of two and four adjacent urban ZIP codes. SCT cases were also centered predominantly in the same two clusters, but slightly more dispersed.

Conclusions: Recent Shelby County birth prevalence estimates differ substantially from national estimates with higher SCD and lower SCT than expected. Preliminary evidence suggests substantial clustering in two small geographic urban areas within Shelby County that may provide target areas for educational and outreach services.