Hemgolobin S-C Disease at the Emory University Georgia Comprehensive Sickle Cell Center at Grady Health System

Introduction

Unlike sickle cell anemia (HbSS disease), little research has been devoted specifically to Hemoglobin SC (HbSC) disease. Though distinct, the disease is often treated simply as a milder form of HbSS disease. As a result, its associated manifestations are less well defined which leads to mismanagement of these patients in the medical community. The aim of this study was to further define HbSC disease and its manifestations, as well as evaluate the burden of chronic opiate use and healthcare utilization in this population.

Design and Methods

A retrospective chart review was performed utilizing patients from one of the largest sickle cell clinics in North America. Patients with hemoglobin electrophoresis confirmed HbSC disease that had been to the center between 2010 and 2016 were identified. Clinical data relating to baseline laboratory values, HbSC disease-related complications and acute care visits was then abstracted from patient's medical records and analyzed to further define this population. IRB approval was granted for this retrospective review.

Results

A total of 210 patients were included in the study. The cohort had a median age of 35 years (mean of 37.2 years, range of 18 to 81 years) and 57.1% were female while 42.9% were male. Steady state laboratory values included an average hemoglobin (HGB) concentration of 11.67 mg/dL. The incidence of chronic complications including chronic opiate use, avascular necrosis (AVN), retinopathy and pulmonary hypertension were 34.76%, 23.33 %, 65.22% (in those with a documented fundoscopic exam) and 2.38% respectively. The incidence of acute complications during the study period including venous thromboembolism, stroke, and acute chest syndrome were 7.62%, 0% and 1.9% respectively. A total of 183 patients (87.1%) had an acute care visit for vaso-occlusive pain crisis during the study period of 6 years (average of 3.51 visits/patient/year) while 113 patients (53.8%) required hospital admission for a vaso-occlusive pain crisis (average of 0.43 admissions/patient/year with an average length of stay of 3.91 nights).

Subgroup analysis comparing those with and without chronic opiate use (more than 3 months chronic pain) revealed similar baseline demographics with median ages of 38 and 33 (average age of 38.5 vs. 36.5, p-value 0.31), respectively. The two groups were also similar in steady state laboratory values (Hemoglobin concentration of 11.69 mg/dL versus 11.65 mg/dL, p-value 0.86) and incidence of AVN (28.77% versus 20.44%, p-value 0.17). However, chronic opiate users did have a significantly higher number of acute care unit visits per year (average of 6.15 versus 1.35, p-value 0.0001) and hospital admissions per year (0.84 versus 0.22, p-value of 0.0001), with chronic opiate users (34.8% of the study population) accounting for 74% of all acute care visits and 71.2% of all hospital admissions.

Conclusions

This cohort helps to further define HbSC disease as a distinct entity from HbSS disease and demonstrates that, though often thought of as mild, this disease places a significant burden on the healthcare system. As expected, the degree of anemia was quite mild compared to that seen in HbSS disease and there were significantly less episodes of stroke and acute chest. However, the incidence of AVN was similar to that seen in HbSS disease and in those with a documented fundoscopic exam the degree of retinopathy was higher, demonstrating one of the characteristics that makes this disease unique. Subgroup analysis of those with chronic opiate use reveals a population with a propensity toward high health care utilization. These distinctions help to identify risks of morbid complications in this population as well as areas to focus efforts in screening and prevention.