Concentration of voxelotor in sickle cell disease can be estimated using electrophoresis and high-performance liquid chromatography.

OBJECTIVES: Voxelotor can increase hemoglobin levels in patients living with sickle cell disease (SCD). A clinician who is monitoring voxelotor response may want to know whole-blood voxelotor concentration, but this cannot be measured in most clinical settings. However, voxelotor has been demonstrated to cause "peak splitting" in common methods of hemoglobin measurement such as capillary zone electrophoresis (CZE) and high-performance liquid chromatography (HPLC). We hypothesized that we could use the size of the peak split to estimate the whole-blood concentration. METHODS: Blood from people with SCD was dosed with known concentrations of voxelotor, and multiparameter regression was used to derive the relationship of voxelotor concentration to the degree of peak splitting observed. To validate these equations, 21 patients started on voxelotor at 1500 mg/d had blood samples drawn at days 0, 14, 30, and 60. Samples were sent out for gold standard voxelotor concentration testing. The derived equations were then used to calculate voxelotor concentration. RESULTS: Calculated concentrations correlated strongly with measured concentrations for both CZE (R2 = 0.83, P < .001) and HPLC (R2 = 0.76, P < .001). Voxelotor concentration also had a significant effect on increases in hemoglobin (R2 = 0.40, P < .001). CONCLUSIONS: Thus, peak splitting CZE and HPLC can be used to estimate voxelotor concentration.

Excess deaths among adults with sickle cell disease in 2020 compared to prior years.

In 2020, there was a 20% increase in excess deaths in the USA due to COVID infections but also to changes in the healthcare system due to the pandemic. We hypothesized that people living with sickle cell disease (SCD) may be vulnerable to these changes as SCD can lead to rapid decompensation. We examined all deaths of people with SCD at our center in 2020. Cause of death was determined, clinical variables, and healthcare utilization, and the presence of COVID infection, sepsis, and acute organ failure during the death event was obtained from the electronic medical record. Deaths in 2020 were compared to deaths in 2017-2019. In 2020, deaths increase 244% (22 vs 9), but acute or previous COVID infections were identified in only 36% of 2020 deaths. People who died in 2020 were more likely to have developed acute organ failure during the death event (70.6% vs 21.1%, p = 0.003) compared to prior years. They were also more likely to have a history of stroke and more frequent hematology clinic visits. Deaths in 2020 doubled compared to prior years and COVID infection could not account for all of this excess mortality. People who died in 2020 may have had more severe disease as suggested by having more clinic visits and higher rates of stroke and were more likely to develop organ failure during the death event. This demonstrates that people with SCD may be especially vulnerable to delays in care. Larger multicenter studies should be conducted to examine this further.

Elevated fetal haemoglobin levels are associated with decreased incidence of retinopathy in adults with sickle cell disease.

Among the many vascular complications of sickle cell disease (SCD), retinopathy is the most prevalent and represents a leading cause of blindness. Hydroxycarbamide therapy ameliorates many symptoms of SCD, and high fetal haemoglobin (HbF) levels have been shown to protect against the development of retinopathy in children with HbSS. Its effect on adults with SCD, who are at a much higher risk of developing retinopathy, has not been studied. We aimed to investigate the effect of hydroxycarbamide use and HbF level on sickle cell retinopathy development in adults. We performed a retrospective cross-sectional study and collected demographics, comorbidities, and ocular and haematological data from 300 adult sickle cell subjects examined at the Henkind Eye Institute at Montefiore Medical Center during a 5-year period, from October 2012 to November 2017. The cohort was comprised mainly of Black and Hispanic subjects with all SCD genotypes, aged 18-71 years. Results show that in HbSS patients treated with hydroxycarbamide, those with retinopathy had significantly lower HbF levels compared to patients without retinopathy (P = 0·018). Our study identified the optimal HbF cut-off point for retinopathy protection to be 14·87%. Thus, a HbF level of 15% appears to be the threshold above which the odds for developing retinopathy in SS patients are reduced by 50%.