Delay in treatment of adult hemophagocytic lymphohistiocytosis is associated with worse in-hospital outcomes.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition characterized by uncontrolled activation of the immune system leading to multiorgan failure. Timely initiation of HLH-specific treatment is believed to be essential and lifesaving. Due to the rarity of the condition in adults, there is no data available in the literature to investigate the effects of treatment delay in this age group. We used data from the National Inpatient Sample (NIS) to evaluate the inpatient practices of HLH treatment initiation over 13 years (2007-2019) and their association with clinically relevant inpatient outcomes. Patients were divided into early treatment group (<6 days) and late treatment group (≥ 6 days). We compared outcomes using multivariate logistic regression models adjusting for age, sex, race, and HLH-triggering conditions. There were 1327 and 1382 hospitalizations in the early and late treatment groups, respectively. Hospitalization in the late treatment group had higher rates of in-hospital mortality (OR 2.00 [1.65-2.43]), circulatory shock (OR 1.33 [1.09-1.63]), requiring mechanical ventilation (OR 1.41 [1.18-1.69]), venous thromboembolism (OR 1.70 [1.27-2.26]), infectious complications (OR 2.24 [1.90-2.64]), acute kidney injury (OR 2.27 [1.92-2.68]), and requiring new hemodialysis (OR 1.45 [1.17-1.81]). Additionally, we observed no significant trend in the mean time to treatment over the study period. This study shows the importance of early initiation of HLH treatment and highlights the adverse outcomes of treatment delay.