Should we longitudinally monitor blood viscosity in patients with sickle cell anemia?

Blood viscosity is recognized as a key determinant in the pathophysiology of vaso-occlusive crises (VOC) in sickle cell anemia (SCA). However, its longitudinal relationship with changes in VOC frequency over time remains poorly understood. The present study analyzed the associations between the changes in blood rheological parameters and the changes (delta) in the rate of VOC over time in 63 SCA patients. VOC rates (calculated over the 3 years preceding each blood sampling) and biological parameters were measured at two separate occasions, spaced by at least 3 yrs. (mean difference between the two measurements: 5.7 ± 2.0 years). A positive correlation was observed between the delta-VOC rate and the percentages of change in white blood cells, lactate dehydrogenase and blood viscosity. A multivariate linear regression was performed to test the independent association between the delta-VOC rate and the percentages of change in these biological parameters. The model was statistically significant (R 2 = 0.47, p < 0.01), and blood viscosity was the only parameter independently associated with the percentage of change in VOC rate (β coefficient = 0.025, 95% CI: 0.009–0.040, p < 0.01). Our study demonstrated that steady-state blood viscosity is a valuable biomarker in SCA, given its associations with temporal variations of VOC frequency.