This was a prospective cross-sectional pilot study that was ancillary to the previously reported leptin study[12] in which 55 SCA patients were enrolled consecutively as they came for care at 5 health facilities in Lagos State, Nigeria. However, this study extended to September 2010, translating to 4 additional months after the leptin study during which 18 new patients were enrolled. Blood samples were collected at enrollment for the parvovirus B19 seroprevalence study.