Health Care Utilization for Painful Events Is Associated with Early Mortality in a Contemporary Population of Adults with Sickle Cell Anemia

Painful vaso-occlusive crises are the most common symptom associated with sickle cell anemia (SCA) and show a large inter-patient variability in the frequency and severity. Historically a high rate of admissions for pain is associated with early mortality in SCA adults. Modern day management of SCA includes screening for life threatening complications such as pulmonary hypertension and disease modifying therapies such as hydroxyurea and chronic blood transfusions. It has also become clear that all acute painful events including some self reported crisis do not lead to ED visit/ hospitalization therefore use of healthcare utilization may underestimate the actual frequency of painful vaso-occlusive crises. The present study determined if ED visit/ hospitalizations for painful vaso-occlusive crises remain a marker of early mortality in the modern era.

To determine the relative contribution of pain and other established risk factors for death in a contemporary adult cohort with sickle cell anemia, we analyzed data of SCA individuals who were evaluated at NIH between February 2001 and June 2007 for screening of the IRB approved protocol to study pulmonary hypertension in sickle cell disease. Self reported history of vaso-occlusive painful events requiring visit to an emergency department (ED) or in-patient hospitalization in 12 months preceding the enrollment was used to stratify study subjects into no-ED visit/ hospitalization or ED visit/hospitalization group. Characteristics between the groups were compared. Doppler echocardiography was used to estimate systolic pulmonary artery pressure through measurement of the tricuspid regurgitation velocity (TRV). Study subjects were followed prospectively and age at death was recorded.

One hundred and four (40%) SCA subjects reported no ED visit/ hospitalization while 160 (60%) reported at least one ED visit/ hospitalization in 12 months preceding the enrollment. Although not statistically significant, a higher proportion of study participants in the ED visit/ hospitalization group were on hydroxyurea (38 vs. 69%; P=0.4), and more likely to have received > 10 red cell transfusions (37 vs. 48%; P= 0.09). The no-ED/ hospitalization group and ED/ hospitalization groups were not different in median age (33 vs. 31; P=0.1) or fetal hemoglobin concentration (7.7 vs. 6.9%; P=0.3). Overall forty (15.1%) individuals died during the median follow-up period of 5 years. Cox proportional hazards analysis was performed to determine if severe pain crisis requiring ED visits/hospitalizations were associated with early mortality after adjusting for other known risk factors for mortality (Table 1). Risk for mortality was significantly associated with a history of severe pain crisis requiring ED visit/hospitalization in preceding year (RR 2.81, 95% CI: 1.2–6.4, P= 0.04), elevated TRV ≥ 3 m/s (RR 4.07, 95% CI: 1.3–12.8, P= 0.02) and elevated ferritin (RR 2.31, 95% CI: 1.0–5.0, P= 0.04).

Severe painful episodes requiring health care utilization are associated with premature mortality and despite likely underestimation of actual frequency of pain, remain a marker of disease severity. Elevated TRV a marker of elevated pulmonary arterial pressure and early mortality has a cumulative effect with pain on reduced survival. Consistent with Cooperative Study of Sickle Cell Disease (CSSCD) report, higher hemoglobin (and lower LDH) was associated with reports of ED visit/ hospitalization likely related to increased viscosity. We conclude that as a group, SCA patients reporting severe pain requiring ED visits /hospitalization and elevated TRV are at the highest risk for shortened survival.

No relevant conflicts of interest to declare.