5613396 DIFFERENCE IN HOSPITALIZATIONS AND ANNUAL BED DAYS FOR PATIENTS WITH SICKLE CELL DISEASE BY VARYING LEVELS OF ANEMIA: A RETROSPECTIVE ANALYSIS OF LINKED PRIMARY AND SECONDARY CARE DATABASES IN ENGLAND

Abstract

Background: Sickle cell disease (SCD) is a life-threatening autosomal-recessive disorder in which the sickle variant of hemoglobin (Hb) polymerizes under deoxygenation, causing red blood cell sickling and hemolytic anemia. Anemia in SCD is associated with an increased risk of complications such as leg ulcers and end-organ damage (EOD), which often require hospitalization, a key driver of healthcare costs. Aims: To quantify differences in all-cause hospitalizations and annual bed days in patients with SCD and differing levels of anemia. Methods: We identified 6018 patients with SCD aged ≥12 years with ≥1 recorded Hb level between January 1, 2007, and March 31, 2019, from the Clinical Practice Research Datalink (Aurum version), an English longitudinal primary care electronic medical record, and linked these with Hospital Episode Statistics, a secondary care reimbursement data set. We obtained Hb levels from primary care records, when disease is expected to be relatively stable, as opposed to during hospitalization. We used Hb measurements separated by <30 days to calculate mean Hb for a time interval at a specific Hb level. Patients were grouped into Hb categories based on having ≥1 Hb record of <6 g/dL (severe anemia), 6 to <8 g/dL, 8 to 10.5 g/dL, or >10.5 g/dL; patient Hb category may have changed over the course of the study. Patient Hb intervals began with Hb in a category and ended on the day before a blood transfusion, with a Hb reading in a new category, or on the last activity date. We compared the significance of the categorical data distribution for hospitalizations using the Kruskal–Wallis test across Hb categories, extended with pairwise Wilcoxon rank sum testing. We repeated the above for hospitalizations due to any EOD and annual bed days. Results: Of 6018 patients with recorded Hb, 72% had a history of Hb >10.5 g/dL, 44% had 8 to 10.5 g/dL, 15% had 6 to 8 g/dL, and 3% had <6 g/dL. The annual rate of all-cause hospitalizations decreased as Hb increased: 5.84 in patients with Hb <6 g/dL, 4.13 for 6 to 8 g/dL, 3.3 for 8 to 10.5 g/dL, and 1.7 for >10.5 g/dL. Hospitalizations were significantly lower for patients with a history of Hb >10.5 g/dL than for those with Hb <6 g/dL (P<0.001); across Hb categories, the distribution of all-cause hospitalization was significant (P<0.001). Annual all-cause bed days decreased across increasing Hb categories, with a mean of 8.8 days in patients with a history of Hb <6 g/dL, 7.7 days with 6 to 8 g/dL, 5.8 days with 8 to 10.5 g/dL, and 3.2 days with >10.5 g/dL. A significant decrease in annual bed days was observed in patients with a history of Hb >10.5 g/dL compared with Hb <6 g/dL (P<0.001). Across Hb categories, the distribution of the difference in bed days was significant (P<0.001) (Figure).A total of 385 patients (6.4%) had ≥1 hospitalization for any EOD. Significantly fewer hospitalizations were attributable to any EOD in patients with a history of Hb >10.5 g/dL compared with those with a history of Hb <6 g/dL (0.36 and 2.4 hospitalizations per patient interval per year, respectively; P<0.001). Summary/Conclusion: All-cause hospitalizations and annual bed days were progressively reduced in patients with a history of higher Hb levels whereas patients with severe anemia did not experience the same benefit. Due to this tendency, appropriate measures should be taken to maximize Hb in patients with SCD. Reference 1. Kato GJ, Piel FB, Reid CD, et al. Sickle cell disease. Nat Rev Dis Primers. 2018;4:18010.