Reliability of isoelectrofocusing for the detection of Hb S, Hb C, and Hb D in a pioneering population-based program of newborn screening in Brazil

Out of 128,326 newborns in the first 6-month period of a population-based s creening program in Minas Gerais, Brazil, a second sample was obtained at t he age of 6 months from 4,635 carriers of Hbs AS, AC, and AD which were det ected by isoelectrofocusing. Discordance in results occurred in only 27 cas es (0.6%): in seven there was a history of hemotransfusion; errors during p ipetting or transcription of results occurred in seven cases; it was diffic ult to differenciate between Hbs S and D in eight patients; and the causes were not elucidated in five patients. The incidence of Hbs FS and FSC for t he total population was 1:2,800 and 1:3,450, respectively. Isoelectrofocusi ng is a very reliable method for distinguishing AS, AC, or AD carriers from patients with presenting variant hemoglobin and beta (+)-thalassemia combi nations, and may be widely used in massive newborn screening programs.