Symptomatic Avascular Necrosis: An Understudied Risk Factor for Acute Care Utilization by Patients with SCD.

OBJECTIVES: Sickle cell disease (SCD) is associated with high healthcare utilization rates and poor outcomes in a subset of patients, although the underlying factors that predict this phenotype are poorly understood. Prior studies suggest that comorbid avascular necrosis (AVN) contributes to high healthcare utilization. We sought to clarify whether AVN independently predicts acute care utilization in adults with SCD and to identify characteristics of those with AVN that predict higher utilization. METHODS: We reviewed the medical records of 87 patients with SCD with symptomatic AVN and compared acute care utilization and clinical characteristics with 87 sex- and age-matched patients with SCD without symptomatic AVN. Patients with ≥2 years of follow-up were included. Outcomes were compared using bivariate analysis and multivariate regression. RESULTS: Our study included 1381 follow-up years, with a median of 7 years per patient. The AVN cohort had greater median rates of urgent care visits (3.2/year vs 1.3/year; P = 0.0155), admissions (1.3/year vs 0.4/year; P = 0.0002), and admission days (5.1 days/year vs 1.8 days/year; P = 0.0007). History of high utilization (odds ratio [OR] 4.28; P = 0.001), acute chest syndrome (OR 3.12; P = 0.005), pneumonia (OR 3.20; P = 0.023), hydroxyurea therapy (OR 2.23; P = 0.0136), and long-term transfusion (OR 2.33; P = 0.014) were associated with AVN. In a median regression model, AVN, acute chest syndrome, and pneumonia were independently associated with greater urgent care visits and admissions. CONCLUSIONS: Symptomatic AVN was found to be an independent risk factor for acute care utilization in patients with SCD. Because this is a potentially modifiable factor, further studies are urgently needed to determine whether AVN prevention/early treatment interventions will alter utilization and improve outcomes for patients with SCD.

Preliminary evidence that hydroxyurea is associated with attenuated peripheral sensitization in adults with sickle cell disease.

INTRODUCTION: Hydroxyurea (HU) is a drug that targets the underlying pathophysiology of sickle cell disease (SCD); however, it continues to be an underutilized treatment for adults. Previous research suggests that HU treatment can result in fewer hospital contacts for acute vaso-occlusive pain crises (VOC). Hydroxyurea's impact on non-VOC pain, however, is not well established. OBJECTIVES: This study examined whether HU moderated patterns of static and dynamic pain processing and clinical pain in SCD individuals. METHODS: Fifty-eight patients with SCD (N taking HU = 17) underwent quantitative sensory testing (QST) and completed twice daily symptom diaries for 12 weeks. Quantitative sensory testing established thermal threshold and tolerance, mechanical thresholds, and thermal and mechanical temporal summation of pain. RESULTS: Groups did not differ in age, sex, or opioid use. After controlling for morphine use, QST results showed that participants taking HU had higher heat and mechanical pain thresholds (static QST measures) but not thermal and mechanical temporal summation (dynamic QST measures). Participants taking HU also reported lower VOC pain compared with SCD participants not taking HU; however, HU did not moderate non-VOC clinical pain ratings. CONCLUSION: Findings cautiously suggest that HU acts on pain hypersensitivity and VOC pain, rather than inhibiting pain facilitation and non-VOC pain. These differences may reflect HU's influence on peripheral rather than central sensitization. Future research is warranted to replicate these findings in a larger sample and determine whether early HU administration can prevent peripheral sensitization in SCD individuals.