A simple and rapid screening test which differentiates sickle-cell trait and sickle-cell anaemia is described. The test utilizes 0·1 ml of whole blood and is based on the low solubility of reduced sickle haemoglobin. Results intermediate between the sickle-cell trait and sickle-cell anaemia are obtained in unusual cases of sickle-cell anaemia with high foetal haemoglobin.The need to supplement the results with haematological and electrophoretic techniques is discusses.

Two sons of a previously reported Ghanaian homozygote for the hereditary persistence of fetal hemoglobin (HPFH) (Ringelhann et al., 1970) also are HPFH homozygotes. In addition, another unrelated adult Ghanaian homozygote has been detected. All of these Ghanaian homozygotes as well as three American Black HPFH homozygotes have the G gamma A gamma type of HPFH with a G gamma to A gamma ratio of about 3:2, in contrast to an Asiatic Indian homozygote who has the G gamma type. Globin chain synthesis in HPFH homozygotes is unbalanced, with a gamma/alpha ratio of 0.6 or less, whereas it is balanced in heterozygotes according to most reports.

Agar gel, cellulose acetate, and starch gel electrophoresis are all capable of diagnosing sickle-cell anaemia, sickle-cell haemoglobin C disease, and haemoglobin C disease in cord blood samples. Of these three electrophoretic techniques, agar gel is the easiest to interpret.Paper electrophoresis can reliably and rapidly detect sickle haemoglobin and haemoglobin C in cord blood samples. Being incapable of differentiating foetal and normal adult haemoglobin, the value of paper electrophoresis is limited to an initial screening procedure.

SummaryHematologic and globin chain synthesis studies have been made in 21 children, aged 2 to 6 years, many of their parents, and several normal adults and a-thalassemia heterozygotes. At birth, 11 children had about 5% hemoglobin (Hb) Bart's, 5 had about 2% Hb Bart's, and 5 had no trace of Hb Bart's. A significant decrease in mean corpuscular volume. (MCV) and mean corpuscular hemoglobin (MCH) values and an increase in the @/a ratio was observed in the first group; microcytosis and hypochromia were absent in the children of the second group although the @/a ratio was significantly increased. The a chain deficiency is familial. Increased a/a ratios were present in many parents although only two parents of children with 5% Hb Bart's at birth had hematologic findings suggestive of the presence of the same type of defect as observed in the children with the larger amount of Hb Bart's at birth. SpeculationIt is postulated that the absence or presence of duplicated Hb, structural genes is the underlying mechanism for the variable a chain deficiency in black infants. Children with about 5% Hb Bart's at birth have the genotype -a/-a or, rarely, the --/aa genotype; when only two Hb, structural loci instead of four are active, a modest deficiency in a chain production will be the result. The presence of the -a/aa genotype could be predicted from the smaH amounts of Hb Bart's at birth and from data of the hemoglobin synthesis analyses in older children and adults; the -a/a genotype however, is also suggested from data obtained by MCH and MCV determinations. It is concluded that although the -a/a genotype always produces Hb Bart's at birth in moderate amounts, the -a/aa genotype may or may not. The rarity of the --/aa genotype in this population is responsible for the absence of the Hb Bart's hydrops fetalis syndrome.