Sir.—We read with interest the report by Drs Rubin and Rowley and the editorial by Dr Miller in the Journal (1979;133:1248-1250 and 1235-1236). There is an apparent misunderstanding about the procedures used to identify newborns with sickle cell anemia and its variants in the New York State Newborn Screening Laboratories. In the presence of Hb S or Hb C on the filter paper blood specimen tested by both cellulose acetate and citrate agar electrophoresis, a repeat blood sample is requested. The repeat specimen (microcapillary) is again tested by both types of electrophoresis before the result is mailed to the physician in charge of the infant in the hospital of birth.
It is unfortunate that citrate agar electrophoresis cannot distinguish between Hb SS, S/β° thalassemia, and Hb S/HPFH, as has been suggested by Dr Miller in his editorial. The Newborn Screening Laboratories are equipped to make diagnoses of Hb SC,