1. A survey of the incidence of abnormal hemoglobins in different racial groups distributed over the island of Puerto Rico was performed. The relation of the rate of destruction of red cells to the presence of abnormal hemoglobin patterns in the affected population was also studied.
2. The abnormal hemoglobins were classified by the difference in paper electrophoretic mobility. Fetal hemoglobin was measured by its resistance to alkaline denaturation. The red cell life span was determined by measuring the survival of erythrocytes labelled with radioactive sodium chromate.
3. A total of 2,089 inhabitants were studied. There were 1,487 white subjects and 602 Negroes. Forty-two individuals were found to harbor abnormal hemoglobins. All but one were Negroes or Negroid of African descent, and their relative numbers agreed closely with the geographical distribution of ethnic groups in the island. Abnormal hemoglobins were found in 2.01 per cent of the entire series of 2,089 persons, but in those considered Negroes or Negroids the incidence of abnormal hemoglobins was 6.8 per cent.
Of the 42 persons showing abnormal hemoglobins, thirty-four or 81 per cent, had hemoglobin S; only two of these had sickle cell anemia. The incidence of the sickle cell trait among the Puerto Rican Negro population was 5.2 per cent; and the incidence of hemoglobin S disease among those harboring the trait was 5.9 per cent.
Eight, or 19 per cent of the abnormal cases had hemoglobin C; only one of these had hemoglobin C disease with clinical hemolytic anemia. The incidence of the hemoglobin C trait among the Puerto Rican Negro population is 1.3 per cent; and the incidence of hemoglobin C disease among those harboring the trait may reach 12.5 per cent.
4. All 42 cases harboring abnormal hemoglobins showed very small quantities of fetal or alkali-resistant hemoglobin ranging from 0.45 per cent to 3.25 per cent, averaging 1.12 per cent.
5. The "apparent" half-life of the red blood cells was found to be 10 days in sickle cell anemia, 7 days in SC disease, 20.6 days in cases of hemoglobin SA, 18.5 days in one case of hemoglobin C disease and 21.5 days in 2 cases of the combination CA. The normal "apparent" half-life in our laboratory is 24.5 days.