Demographics, Treatment Outcomes and Resource Utilization Among Patients Hospitalized with Adult Onset Hemophagocytic Lymphohistiocytosis (HLH): A Nationwide Analysis

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disease in which impaired natural killer and cytotoxic T-cell function results in excessive immune activation. It is predominantly seen in children; most of the available data comes from the pediatric population so it cannot be generalized to adult HLH. Treatment of HLH usually involves either treating the underlying cause in the secondary form (i.e. malignancy with chemotherapy, rheumatologic with immune suppression) or chemotherapy and stem cell transplantation for primary, familial etiology, multiple courses of intensive chemotherapy, with stem cell transplantation for relapse and familial disease. Recently, increasing adult HLH cases have been reported. The goal of this study is to describe the association between patient factors, geography, hospital resource utilization, and mortality among adult HLH patients.

Methods: We performed a retrospective cohort analysis of the National Inpatient Sample 2012, 2013 and 2014 Databases (HCUP-NIS). Patients were included in the study if they had a principal diagnosis of HLH and were older than 18 years. We used descriptive statistics to characterize the cohort in terms of personal demographic factors (age, race, sex, insurance type, community-level income level), hospital characteristics (size, region, teaching status, and urban or rural location), and admission timing (weekend or weekday). We performed univariate and multivariate regression to analyze the association of the following factors with length of stay and mortality: age, sex, Charlson index, hospital region (Northeast NE, Midwest MW, South, West), income, insurance, hospital size, weekend versus weekday, hospital location (rural versus urban), teaching status. All analyses applied the HCUP-NIS weights.

Results: The cohort comprised 760 patients, the majority of whom were male (57.9%), aged 21-30 years (26.3%), white (56.3%), and treated in large (78.9%) and/or teaching (92.1%) hospitals, third quartile for median household income (30.4%), covered by private insurance (43.4%), and treated in the southern US (32.2%). Per hospitalization, the average total hospital charges were $210,526 (95% CI $176,251 to $244,801) and the average length of stay (ALOS) was 18 days (95% CI 16 to 20). On multivariate analysis, ALOS was significantly longer with patients at teaching hospitals (AMD 5.10 95% CI 0.57 to 9.64, p=0.03) or with self-pay status (AMD 29.05 95% CI 21.62 to 36.48, p <0.01). Coverage with private insurance was associated with reduced ALOS (AMD -5.04 95% CI -10.19 to 0.11, p=0.05). Hospital charges was lower with age (AMD -4434 95% CI -7786 to -1082, p=<0.01); however Charlson index increased hospital charges (AMD 33876 95% CI 6043 to 61708, p=0.02). For mortality, age (OR 1.03, 95% CI 1.01-1.05, p=0.002), Charlson index (OR 1.29, 95% CI 1.05-1.57, p=0.013), and Medicaid coverage (OR 0.19, 95% CI 0.049 to 0.698, p=0.013) were statistically significant on univariate analysis, however only age (OR 1.02 95% CI 1.00 to 1.04, p=0.045) was statistically significant on multivariate analysis.

Discussion: HLH in adults remains a rare disease which requires prolonged hospitalization and high resource utilization. Receiving care in teaching hospitals increases the length of stay most likely reason is that sicker and more complex patients often end up at teaching hospitals. Private insurance coverage reduced ALOS and self pay increased it. We hypothesize that the shorter ALOS with private insurance is due to increased scrutiny by the insurance provider, while the longer ALOS with self pay is related to difficulties ensuring outpatient follow up. In addition, we hypothesize that the decrease in hospital charges with increasing age may be because of early mortality among these patients. However, further studies are required to investigate the above noted associations.

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