Retrospective study of haemophagocytic syndrome hospitalisations in children in the USA

Epidemiology, characteristics, and outcomes of adult haemophagocytic lymphohistiocytosis in the USA, 2006-19: a national, retrospective cohort study

Background

Haemophagocytic lymphohistiocytosis (HLH) is a rare and life-threatening syndrome characterized by an excessive inflammatory response. Limited data exist on adult HLH.

Methods

In this national, retrospective cohort study, we analysed data from the US National Inpatient Sample database collected between October 1, 2006 and December 31, 2019. Using the International Classification of Diseases (ICD) codes, we identified all adult patients who were admitted non-electively with the diagnosis of HLH. We described demographic characteristics, triggers, and associated conditions. Trends of diagnosis, treatment, and in-hospital mortality were analysed using joinpoint models. In-hospital mortality rates were compared using multivariable logistic regression models that adjusted for demographic characteristics and associated conditions. Finally, we described resource utilization outcomes including cost of hospitalization and length of stay.

Findings

We identified 16,136 non-elective adult HLH admissions. The population pyramid showed a bimodal distribution, with peaks in young adults (16-30 years) and older adults (56-70 years). Joinpoint regression analysis revealed a significant increase in HLH incidence per 100,000 admissions over the study period (Average Annual Percent Change [APC] = 25.3%, p < 0.0001), and no significant change in rates of in-hospital mortality (slope = -0.01; p = 0.95) or administration of in-hospital HLH treatment (slope = 0.46, p = 0.20). The most common associated conditions were malignancy (4953 admissions [30.7%]), infections (3913 admissions [24.3%]), autoimmune conditions (3362 admissions [20.8%]), organ transplant status (639 admissions [4%]), and congenital immunodeficiency syndromes (399 admissions [2.5%]). In-hospital mortality was higher in older adults and males. Furthermore, Congenital immunodeficiency syndromes had the worst in-hospital mortality rate (mortality rate 31.1%, adjusted OR 2.36 [1.56-3.59]), followed by malignancies (mortality rate 28.4%, adjusted OR 1.80 [1.46-2.22]), infections (mortality rate 21.4%, adjusted OR 1.33 [1.10-1.62]), other/no trigger (mortality rate 13.6%, adjusted OR 0.73 [0.58-0.92]), autoimmune (mortality rate 13%, adjusted OR 0.72 [0.57-0.92]), and post-organ transplant status (mortality rate 14.1%, adjusted OR 0.64 [0.43-0.97]). The overall mean length of stay was 14.3 ± 13.9 days, and the mean cost of hospitalization was $54,900 ± 59,800.

Interpretation

We provide insight into the burden of adult HLH in the USA. The incidence has been increasing and the outcomes remain dismal. This signifies the growing need for the development of updated diagnosis and treatment protocols that are specific to adult HLH.

Funding

None.

Temporal Trends in the Incidence of Hemophagocytic Lymphohistiocytosis: A Nationwide Cohort Study From England 2003-2018

Hemophagocytic lymphohistiocytosis (HLH) is rare, results in high mortality, and is increasingly being diagnosed. We aimed to quantify the incidence of diagnosed HLH and examine temporal trends in relation to age and associated diseases. Using national linked electronic health data from hospital admissions and death certification cases of HLH that were diagnosed in England between January 1, 2003, and December 31, 2018. We calculated incidence rates of diagnosed HLH per million population by calendar year, age group, sex, and associated comorbidity (hematological malignancy, inflammatory rheumatological or bowel diseases [IBD]). We modeled trends in incidence and the interactions between calendar year, age, and associated comorbidity using Poisson regression. There were 1674 people with HLH diagnosed in England between 2003 and 2018. The incidence rate quadrupled (incidence rate ratio [IRR] 2018 compared to 2003: 3.88, 95% confidence interval [CI] 2.91 to 5.28), increasing 11% annually (adjusted IRR 1.11, 95% CI 1.09 to 1.12). There was a transition across age groups with greater increases in those aged 5-14 years of HLH associated with rheumatological disease/IBD compared with hematological malignancy, with similar increases in HLH associated with both comorbidities for those 15-54, and greater increases in HLH associated with hematological malignancies for those 55 years and older. The incidence of HLH in England has quadrupled between 2003 and 2018. Substantial variation in the incidence occurred with inflammatory rheumatological diseases/IBD-associated HLH increasing more among the younger age groups, whereas in older age groups, the largest increase was seen with hematological malignancy-associated HLH.

Hemophagocytic Lymphohistiocytosis Hospitalizations in Adults and Its Association With Rheumatologic Diseases: Data From Nationwide Inpatient Sample

OBJECTIVE

Hemophagocytic lymphohistiocytosis (HLH) is a rare potentially fatal multisystem inflammatory condition that is often triggered by an underlying medical condition. Epidemiologic data of HLH in adults with rheumatologic diseases are limited. The aim of our study was to characterize HLH hospitalizations in the US adult population with a special focus on patients with concomitant rheumatologic diseases.

METHODS

We conducted a medical records review of hospitalizations in the United States during 2016 and 2017 with a diagnosis of HLH. Hospitalizations were selected from the National Inpatient Sample. International Classification of Diseases, Tenth Revision codes were used to identify rheumatologic diseases. A multivariate logistic regression analysis was used to calculate adjusted odds ratios (ORadj) for the association of HLH and rheumatologic diseases.

RESULTS

Seven hundred fifty hospitalizations had a principal billing diagnosis of HLH. The median age of our study population was 47.5 years, and males made up 55% of the population. Overall mortality was 17%, and the median length of stay was 12 days. Twenty-five percent of the HLH cases had a concomitant rheumatologic diagnosis. Multivariate logistic regression analysis showed systemic lupus erythematosus (SLE) with nephritis (ORadj, 5.7), SLE without nephritis (ORadj, 9.2), adult-onset Still disease (ORadj, 338.9), and ankylosing spondylitis (ORadj, 10.7) were significantly associated with HLH.

CONCLUSIONS

This analysis represents the largest sample to date to assess HLH hospitalizations. Our study showed that SLE, adult-onset Still disease, and ankylosing spondylitis were strongly associated with HLH.

Outcomes of adult critically ill patients with hemophagocytic lymphohistiocytosis in united states-analysis from an administrative database from 2007 to 2015

BACKGROUND

Severe infections caused by the novel coronavirus 2 display similarities to secondary hemophagocytic lymphohistiocytosis (HLH). However, HLH is a rare disease and has not been well described in critically ill patients.

METHODS

We used the Nationwide Inpatient Sample (NIS), the largest all-payer inpatient care database publicly available in the United States to identify all adult discharges with Hemophagocytic syndrome (ICD-9 CM code 288.4) between 2007 and 2015. Critical illness was considered present if patient had either ICD-9 CM code indicating the requirement of invasive mechanical ventilation or the presence of shock. We used ICD-9-CM codes to identify various infections (inf-HLH), malignancies (mal-HLH) and autoimmune diseases associated with HLH (MAS-HLH) and classified them in their respective groups. Primary outcome was in-hospital mortality in critically ill patients. We developed multivariable regression model to examine variables associated with mortality in critically ill HLH patients. P value was kept at < 0.05.

RESULTS

Of the 7420 (95% CI 6959-7881) estimated discharges with HLH, 2313 (31%) were critically ill. Of the critically ill patients, 442 (34%) were mal-HLH, 422 (43.3%) were inf-HLH, 403 (30.7%) were MAS-HLH and 1046 (27.3%) were unable to be classified. In hospital mortality rates were 6.4% in non-critically ill and 48.4% in critically ill patients. Among the subtypes of HLH, in-hospital mortality was 53% in mal-HLH, 49.4% in inf-HLH, 26% in MAS-HLH and 54.6% in unclassified group. On multivariable regression analysis, development of acute renal failure requiring hemodialysis (OR 2.06, 95% CI 1.29-3.3, P=0.002) and acute hepatic failure (OR 2.21, 95% CI 1.38-3.52, P=0.001) were significantly associated with higher mortality.

CONCLUSION

Inpatient mortality of critically ill patients is remarkably high. Patients with MAS-HLH had better outcomes when compared to other groups of HLH.