Hemoglobin Phenotypes in Nigeria: Data From a National Reference Laboratory

Abstract On a global scale, 5% to 7% of the population carries an abnormal hemoglobin. With a sickle hemoglobin (HbS) carrier prevalence of 25% to 40%, Nigeria bears the greatest burden of sickle cell disorder worldwide. Until recent times, detection of other clinically significant hemoglobin variants associated with HbS has been unavailable, resulting in missed/wrong diagnosis, weak national data, and suboptimal control of hemoglobin disorders. This study aimed to review hemoglobin assays over a 2-year period at a national reference laboratory in Nigeria, in order to describe the prevalent hemoglobin phenotypes for health planning. The study was a retrospective, laboratory data-based survey. Sociodemographics and hemoglobin assay results of 6,851 specimens between January 2016 and December 2017 were analyzed. Study protocol was approved by the Institutional Review Board. Participants aged less than 1 year and who had recent transfusions and a history of hydroxyurea therapy were excluded. At the hemoglobin laboratory, specimens were analyzed using cation exchange high-performance liquid chromatography (CE-HPLC) (Bio Rad D10, California). When indicated, further analysis of suspected abnormal hemoglobins was confirmed using a second method, capillary electrophoresis (SEBIA Capiflex II, France). The distribution of the identified hemoglobin phenotypes was determined as a proportion of the total number of participants. The mean (SD) age of the participants was 31.8 (14.9) years. The most frequent hemoglobin phenotypes were AA (59.4%), AS (23.3%), and SS (13.3%). Hemoglobin phenotypes AC (2.1%), SC (0.9%), AGPhiladelphia (0.2%), and CC (0.2%) were less frequent. Least occurring phenotypes were ADIbadan, AE, AGPhiladelphia, AOArab, DD, and hereditary persistence of fetal hemoglobin (HPFH). In the Nigerian context, accurate diagnosis of hemoglobin variants using quantitative, high-resolution hemoglobin assays, compared to zone (cellulose acetate) electrophoresis at alkaline pH will provide data for health planning, better access to genetic counseling, informed reproductive health choices, and secondary prevention of hemoglobinopathies.