More definitions in sickle cell disease: Steady state v base line data

Abstract

Ballas et al. [1] published concise definitions of the complications of sickle cell disease (SCD). There are other definitions that pertain to SCD that are not complications of the disease as such but are associated with establishing the accurate diagnosis, management, and natural history of each complication. Definition of the steady state and of baseline clinical features and lab data are two such examples. These are important in detecting any significant acute change in the clinical picture or any change after the initiation of therapeutic modalities. No history of an acute painful episode that required treatment in the emergency department or in the hospital for at least four consecutive weeks after a previous painful crisis. No history of admission to the hospital or emergency department 2–3 days after the point in time in question. Previous studies showed that the number of irreversibly sickled cells increases and RBC deformability decreases 2–3 days before admission to the hospital in crisis [2]. This change coincides with the prodromal phase of the acute painful crisis described in children and adults [3, 4]. No history of blood transfusion during the previous 4 months of the point in time. Alternately, the % of Hb A determined by electrophoresis or by high performance liquid chromatography must be ≤10%. The exception would be in patients with sickle-β+-thalassemia in whom endogenous Hb A could be as high as 30%. In these patients, history of recent blood transfusion could be obtained from the blood bank that usually supports the institution in question. Patients on chronic blood transfusion or exchange transfusion may be exempt from this requirement or their Hb S steady state level could be the average of 3 determinations of the % of Hb S before scheduled transfusion or exchange transfusion. No history of intercurrent illness such as infection, inflammation during the previous 4 weeks. No treatment with medications such as antibiotics that may affect the blood counts during the previous 3 weeks. The steady state values may change with time. It is, therefore, advisable to determine them periodically every 2–3 years. Knowing the steady state values is extremely important in evaluating patients who present themselves with acute episodes. Comparing data during the acute event with the steady state values often reveals objective changes during crisis. Baseline values include clinical and lab data determined before the initiation of therapy or other interventions. They do not need to meet the requirement of steady state values. Occasionally, they could be the same as steady-state values especially in patients who have relatively mild disease with infrequent painful episodes. Baseline values are markers of the effect of an intended intervention whereas steady-state values are markers of the disease itself. Samir K. Ballas*, * Department of Medicine Cardeza Foundation for Hematologic Research Jefferson Medical College Philadelphia, Pennsylvania.