Cooperative Study of The Clinical Course of Sickle Cell Disease

BACKGROUND:

Sickle cell anemia (Hb SS) and related hemoglobinopathies involving sickle hemoglobin (HbS) had been recognized for many years and numerous clinical and laboratory manifestations had been described. However, the clinical course of sickle cell disease was poorly documented. The ability to establish concrete interrelationships among signs, symptoms and laboratory test results was complicated by the complexity of the interaction of basic disease processes with other health related events.

Comprehensive evaluations of the clinical status of patients were usually carried out only during hospitalizations for 'crises' or other acute illnesses. Because of this inconsistent nature of the doctor/patient relationships, methods of periodic recording of the patient's status needed to be established. Further, the obtaining of comprehensive laboratory data was necessary during periods of apparent clinical remissions as well as hospitalizations. A well designed, statistically valid, longitudinal study could make a significant contribution to a better understanding of sickle cell disease. Information was particularly lacking on the clinical course starting at birth. Criteria needed to be formulated that could establish classifications of organ involvement and severity of the disease processes. Such classifications could ultimately be used in establishing the need for and evaluating the efficacy of proposed therapies.

The source of the idea for the study dates back to 1971 when the Hematology Study Section recommended in a position paper a study on the natural history of sickle cell disease. The Hemolytic Disease Study Group of the Division of Blood Diseases and Resources developed a detailed protocol in 1973. The National Sickle Cell Disease Advisory Committee endorsed the idea in 1975. In April 1976, the Red Cell Working Group of the Blood Diseases and Resources Advisory Committee recommended initiating the study. The National Heart, Lung, and Blood Advisory Council approved the initiative in December 1976.

Phase I, the Planning Phase, began in 1977. The protocols and Manual of Operations were developed in this phase. Phase II, the Enrollment Phase, began in March 1979 and ended in March 1981, except for infants younger than 6 months of age, who continued to be enrolled after March 1981. In 1983 the study was extended for an additional five years through 1988. Beginning in 1989, as a separate initiative, the study follows selected patient groups from the original study for an additional five years. The selected groups include the newborn cohort and patients surviving beyond age 35.