# Effect of Blood Purification on Early Response in Children With Hemophagocytic Lymphohistiocytosis

## TL;DR

This study shows that combining blood purification with standard treatment improves survival in children with severe hemophagocytic lymphohistiocytosis.

## Contribution

The study introduces evidence that combining blood purification with HLH-94/04 improves outcomes in children with HLH and multi-organ dysfunction.

## Key findings

- Combining blood purification with HLH-94/04 improved survival in patients with multi-organ dysfunction.
- Early complete remission at 4 weeks was a strong predictor of overall survival.
- Blood purification monotherapy had the lowest survival rates among all treatment groups.

## Abstract

To evaluate the impact of blood purification (BP) therapy on early treatment response and overall survival (OS) in paediatric haemophagocytic lymphohistiocytosis (HLH). We retrospectively reviewed HLH cases from 2012 to 2022, comparing outcomes among patients treated with the HLH‐94/04 protocol, BP monotherapy, BP combined with HLH‐94/04 (BP + HLH‐94/04), or other regimens. A matched subgroup analysis was conducted in patients with multi‐organ dysfunction syndrome (MODS) to assess survival differences. Cox regression identified prognostic factors, and mediation analysis evaluated the contribution of complete remission (CR) at 4 weeks to OS. A total of 102 patients were included, five with primary HLH. Among them, 53 received HLH‐94/04, 13 received BP monotherapy, 22 received BP + HLH‐94/04, and 14 received other treatments. OS differed by treatment: HLH‐04 (81.3%), HLH‐94 (76.6%), other regimens (47.6%), BP + HLH‐94/04 (23.4%), and BP monotherapy (15.4%) (p < 0.001). In MODS patients, survival was 37.5% (HLH‐94/04), 30.8% (BP + HLH‐94/04), and 8.3% (BP monotherapy) (p = 0.013). Among partial/non‐responders (PR/NR) at 4 weeks, survival occurred only in the HLH‐94 group (28.6%) (p = 0.018); in PR/NR with MODS, only BP + HLH‐94/04 showed survival (18.2%) (p = 0.008). CR at 4 weeks, central nervous system involvement, and elevated lactate dehydrogenase were independent predictors of OS (p < 0.05). Mediation analysis showed CR contributed 79.88% to OS in BP + HLH‐94/04 and 33.28% in BP monotherapy. BP combined with HLH‐94/04 may improve survival in patients with MODS or poor early response. Early CR at 4 weeks is a key prognostic marker.