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Sickle cell disease (SCD), a group of inherited disorders that affect hemoglobin (Hb), is the most common monogenic disorder and affects millions of people worldwide. In the USA, the number of people with SCD is about 100,000, and additional 3 million people carry sickle cell trait [1]. The impact of hemoglobinopathies on healthcare is considerable and has great social and economic consequences. Washington, District of Columbia (DC), with its southern Maryland and northern Virginia suburbs, is home to a large population of African Americans that include descendants of forced emigration from Africa in the trans-Atlantic slave trade and more recent immigrants. It is estimated that one in 365 American blacks has SCD, and one in 12 carries the HbS gene (sickle cell trait) [1]. Major sickle cell mutations of the β-globin gene are Glu6Val that leads to HbS [2], Glu6Lys that produces HbC [2] and Glu26Lys that generates HbE [3]. Over 1,300 Hb variants are known of which only a few are considered clinically relevant. HbSS is the most serious phenotype. Here we estimated the frequency of the sickle cell variants in metropolitan Washington, DC. from a retrospective study of individuals who were screened at Howard University Center for Sickle Cell Disease during the period 2009 2018. We acquired blood samples from individuals who attended our free screening service that we provided at Howard University or through community-based outreach programs and health fairs. Participation was voluntary and no restriction was placed on age, demography, gender or ethnicity. Hemoglobin screening program was approved by Clinical Laboratory Improvement Amendments (CLIA) and we obtained written consent from participants. Retrospective analysis of the de-identified collected data was approved by the Institutional Review Board of Howard University. Blood samples were collected by minimally invasive finger prick. Testing was completed in the CLIA-certified laboratory at Howard University Center for Sickle Cell Disease. Expression level of Hb variants F, A, A2, S and C were determined by high-performance liquid chromatography (HPLC) using Ultra2 Variant System (Trinity Biotech, Jamestown, NY, USA). Samples were processed using a high-resolution method, which requires about 10 min run time per sample, thus allowing for higher sensitivity and specificity in identifying rare Hb variants. We asked participants for demographic data including age, gender, ethnic grouping and residence and contact information. Individuals whose analysis by HPLC indicated a Hb variant were contacted and offered genetic counseling. They were further given referral to a hematologist for confirmation and follow-up as needed. Inferential statistics was based on an assumption of Poisson distribution. We analyzed blood samples from 3,677 voluntary participants. Of those participants who responded fully to the questionnaire for demographic information, 67% were female and 33% were male (Supplementary Material 1a, www.thejh. org). The majority of participants (88.8%, 2,283) identified themselves as African American or black, while 4.7% (122) identified themselves as Hispanic Americans and 6.5% (166) responded as other (Supplementary Material 1b, www.thejh. org). Eight hundred thirty-seven participants (26.7%) did not state their race. Our study participants were all adults and uniformly distributed in age from 18 to 66 years and above (Supplementary Material 1c, www.thejh.org). The median (interquartile range) age was 48 (33 59) years. About half of the participants (52.8%, 1,785) lived in the DC, and nearly all the rest (48.7%, 1,305) resided in southern Maryland. A small number (6.1%, 206) were from counties in northern Virginia (Supplementary Material 1d, www.thejh.org). As expected, the predominant majority of the screened Manuscript submitted January 7, 2020, accepted January 30, 2020 Published online August 14, 2020

Prevalence of Sickle Cell Trait and Rare Hemoglobin Variants in the Metropolitan Washington DC Area