Clinical correlates of steady-state oxyhaemoglobin desaturation in children who have sickle cell disease

Individuals with sickle cell disease (SCD) may have oxyhaemoglobin desaturation during the steady-state, the causes of which are incompletely known. We studied a cohort of 585 children who have sickle cell anaemia (SS), sickle beta(0)-thalassaemia (S beta(0)), sickle-haemoglobin C disease (SC), or sickle beta(+)-thalassaemia (Sb+) to determine the relationships between steady-state oxyhaemoglobin saturation (SpO(2)) and SCD genotype, age, gender, steady-state haemoglobin (Hb) and reticulocyte count, and rate of acute chest syndrome (ACS). The SS/S beta(0) group (n 390) had lower mean SpO(2) than the SC/S beta(+) group (n 195) (96.3% vs. 98.7%, P < 0.001). Among SS/Sb-0 subjects, a decrease in steady-state SpO(2) correlated with a decrease in Hb, an increase in reticulocytes, older age and male gender. These correlations were not found in the SC/Sb+ group. Prior ACS did not correlate with steady-state SpO(2). A multivariate model explained 45% of the variability in SpO(2), but only 5% of the variation in SpO(2) was explained by Hb. We conclude that steady-state desaturation is common in individuals with SCD, but it appears to be unrelated to prior episodes of ACS and largely unexplained by chronic anaemia.