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

Abstract

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 beta0-thalassaemia (Sbeta0), sickle-haemoglobin C disease (SC), or sickle beta+-thalassaemia (Sbeta+) to determine the relationships between steady-state oxyhaemoglobin saturation (SpO2) and SCD genotype, age, gender, steady-state haemoglobin (Hb) and reticulocyte count, and rate of acute chest syndrome (ACS). The SS/Sbeta0 group (n = 390) had lower mean SpO2 than the SC/Sbeta+ group (n = 195) (96.3% vs. 98.7%, P < 0.001). Among SS/Sbeta0 subjects, a decrease in steady-state SpO2 correlated with a decrease in Hb, an increase in reticulocytes, older age and male gender. These correlations were not found in the SC/Sbeta+ group. Prior ACS did not correlate with steady-state SpO2. A multivariate model explained 45% of the variability in SpO2, but only 5% of the variation in SpO2 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.

Fig 1

Histograms of steady-state oxyhaemoglobin saturation, SpO₂ by sickle cell disease genotype. Panel (A) depicts subjects with either sickle cell anaemia or sickle β⁰-thalassaemia. Panel (B) depicts subjects with either sickle-haemoglobin C or sickle β⁺-thalassaemia.

Fig 2

Bivariate correlations between steady-state oxyhaemoglobin saturation (SpO₂) and other variables by sickle cell disease genotypes. Panel (A) shows the correlation between Hb (Hgb) and SpO₂ among sickle cell anaemia (SS, grey circles) and sickle β⁰-thalassaemia (Sβ⁰, black squares) subjects. Panel (B) shows the correlation between Hb (Hgb) and SpO₂ among sickle-haemoglobin C (grey circles) and sickle β⁺-thalassaemia (Sβ⁺, black squares) subjects. Panel (C) illustrates the correlation between SpO₂ and age among SS and Sβ⁰ subjects. Panel (D) depicts the lack of correlation between SpO₂ and rate of acute chest syndrome among SS and Sβ⁰ subjects.