Pre-End Stage Kidney Disease Care for Adults with Sickle Cell Disease Living in California

Background: Chronic kidney disease (CKD) is an independent risk factor for mortality in sickle cell disease (SCD). SCD patients who progress to end-stage kidney disease (ESKD) have a poor prognosis, with an estimated 26% mortality rate in the first year of starting renal replacement therapy. Limited access to nephrology care has previously been shown to further contribute to the morbidity and mortality associated with ESKD in SCD (McClellan AC, et al. 2012). However, contemporary data regarding access to care pre-ESKD are limited.

Methods: We performed a retrospective cohort study of Medicaid-enrolled SCD patients in California, aged 18 and older, with an ICD-9/ICD-10 diagnosis code for ESKD. Data sources included Medicaid claims, Emergency Department (ED) visits, hospitalizations, and mortality data from 2011 to 2020, obtained from the California Sickle Cell Data Collection program. Outpatient encounters with hematologists and nephrologists were identified using the National Provider Identifier of the rendering provider. Linked death records were used to identify deaths that occurred during the study period.

The cohort was further stratified to identify patients with data for 1 and 3 years prior to ESKD diagnosis, aiming to evaluate ESKD risk factors and assess the severity and complications of SCD during these periods. The hazard ratio (HR) was calculated by comparing the one-year post-ESKD mortality rates between SCD patients with and without nephrology visits in the year prior to ESKD diagnosis. The 95% confidence interval for the HR was calculated using the standard error of the logarithm of the HR.

Results: From 2011 to 2020, we identified 238 SCD patients with ESKD, of whom 52.1% were female. The median age at ESKD diagnosis was 47.9 years (IQR 38-57). Of the 238 patients, 167 had data for at least 1-year before the first ESKD ICD code (pre-ESKD cohort; 53.2% female), and 127 had data for 3-years prior to first ESKD ICD code.

Risk factors for ESKD included hypertension (77.8%), diabetes mellitus (18.0%), and obesity (22.1%). In the pre-ESKD cohort, hydroxyurea was used by 29 patients (17.4%), and 15 patients (8.9%) received at least one dose of erythropoiesis-stimulating agent (ESA). Simple transfusions were given to 48 patients (28.7%), and a small number (<11 patients) received exchange transfusions.

In the 3-years leading up to ESKD, the hospitalization and ED visit rates were 2.78 and 3.92 visits per person-year, respectively, increasing to 4.02 and 5.22 visits per person-year in the year preceding ESKD diagnosis (p-value < 0.05). Access to specialty care in the year before ESKD was limited; 34 patients (20.3%) had both hematology and nephrology visits, 58 patients (34.7%) had nephrology visits only, and 60 patients (35.9%) had hematology visits only. Dialysis access was placed in 23 patients (13.7%) only in the year leading to ESRD diagnosis.

In the entire cohort, during the 10-years period, there were 115 deaths (48.3%) with a median time to death post-ESKD diagnosis of 16 months (IQR 5-41). Forty-nine patients (20.6%) and 81 patients (34.0%) have died at 1-year and 3-years post-ESKD, respectively. Patients with pre-ESKD nephrology visits had a longer median time to death of 17 months (IQR 2-36), compared to 11 months (IQR 2-28.5) for those without. The median time to death for those with pre-ESKD hematology visits was 9.5 months (IQR 1-25), versus 15 months (IQR 5-36) for those without. Patients with both hematology and nephrology visits, had a median time to death of 17 months (IQR 4-25), compared to 13 months (IQR 3-30) for those without visits. The unadjusted HR for mortality in SCD patients with pre-ESKD nephrology visits, compared to those without, was 0.58 (95% CI 0.25, 1.33).

Conclusion: This descriptive analysis of SCD patients with ESKD in California highlights significant care gaps and disparities. There is a substantial burden of ESKD, with only a small percentage of patients receiving transfusions, hydroxyurea, or ESA therapy. Despite an increase in acute care use in the year preceding ESKD diagnosis, access to hematology and nephrology specialty care remained severely limited. Patients with pre-ESKD nephrology care showed a trend toward improved survival. This study represents a crucial step in addressing the healthcare system gaps and sets the stage for further investigation to improve management for this underserved population.

Gopal:Agios Pharmaceuticals, Inc.: Research Funding; Pfizer: Research Funding.