Does Adherence to Hydroxyurea Affect Emergency Department Observation Unit Utilization?

Background: Emergency department observation units (EDOUs) allow for rapid initiation of analgesic treatment for sickle cell disease (SCD) patients during a vaso-occlusive crisis (VOC) without admitting the patient to the hospital. This research takes place at an EDOU that was created in 2006 at a Tertiary ED and follows standard pain management guidelines for up to 24 hours; at which point the patient is admitted to the hospital or discharged home. The EDOU is utilized when the patient is unable to control VOC pain at home. Outside the ED, the SCD population is treated at the local Sickle Cell Center. Consistent outpatient visits provide patients with information and prescriptions to manage their VOC at home reducing the need to go to the hospital. Patients with SCD are routinely prescribed narcotics for short-term pain management and hydroxyurea (HU) to improve long-term health outcomes. HU is known to decrease pain and hospitalizations

Objective: Compare HU adherent and non-adherent patients’ utilization of the EDOU, outpatient SCD visits, and hospital admissions. 

Methods: This study was a retrospective chart and database review.  The study used patients’ medical charts and a database that contained a record of the visits of patients with SCD to the EDOU between September 2013 and May 2015, for a total of 21 months of observation. A total of 727 EDOU visits generated by 154 patients were reviewed for inclusion in the study. Inclusion criteria consisted of 21 months of pharmacy records and no contraindication for HU administration. A record of pharmacy charges was collected using the EMR, this pharmacy data was also used to determine that the patient was living in the area during the entire time of the study and was filling prescriptions locally.  Additionally, the following data were collected; hospital admissions, outpatient visits to the Sickle Cell Center and monthly refills of HU. The study was approved through expedited review by the institution’s Institutional Review Board (IRB). 

Results: The visits of 14 patients were excluded because a review of clinical notes determined that each of these patients was not prescribed HU because of contraindication or mild disease.  Seventy patients were excluded from the study because there was not consistent pharmacy data to confirm local residency during the time of the study.  The visits of 70 patients (44 HbSS, 18 HbSC, 5 HbSβ⁰-thal, 3 HbSβ⁺-thal) met the inclusion criteria and were included in the analysis.

Patients who refilled their HU prescription 50% or more of the time were considered to be adherent with treatment (n=8). Fifty percent was used as a cutoff point to indicate the likelihood that the patient was experiencing some level of therapeutic benefit. Adherence to HU was determined via pharmacy records and clinical notes. Sixty-two patients refilled their HU prescription less than 50% of the time during the months of the study and were considered to be non-adherent.  The number of EDOU visits between the two groups was compared. The mean value of EDOU visits was 7.1 in the non-adherent group, and 2.4 in the adherent group. A two-sample t-test with unequal variance showed the number of EDOU visits in the adherent group was significantly lower than the non-adherent group (p=6.049E-5). The mean value of admittance between the two groups was not statistically significant nor was the mean value of outpatient visits (8.6 for the non-adherent group and 10.9 visits for the adherent group).

Conclusion: Analysis of the data show that 93% of SCD patients in the study were encouraged or prescribed to take HU, however only 11% are adherent and take HU frequently enough to achieve some level of therapeutic benefit. The eight patients who met the adherence criteria for HU utilized the EDOU less frequently. This same patient population had 12% more outpatient visits within the study time frame. While the difference in outpatient clinic visits between groups was not statistically significant these additional visits could have also had a positive impact on patient well-being. This study supports the idea that HU adherence can reduce VOCs leading to fewer visits to the EDOU. This study was designed to provide insight on a SCD patient population that frequents an EDOU.  A better understanding of this population, particularly in terms of HU compliance, provides physicians insight into providing more effective care to SCD patients to prevent VOCs and reduce EDOU visits.