Clinical Significance of Cerebrospinal Fluid Soluble CD25 in Pediatric Hemophagocytic Lymphohistiocytosis with Central Nervous System Involvement

Objective: To analyze the clinical significance of soluble CD25 (sCD25) levels in cerebrospinal fluid (CSF) in pediatric hemophagocytic lymphohistiocytosis (HLH) with central nervous system (CNS) involvement.

Methods: All patients diagnosed with HLH admitted to Beijing Children's Hospital, Capital Medical University between January 1, 2017 and October 31, 2021 who received a measurement of their HLH-related parameters and CSF sCD25 levels at admission were enrolled in this study.

Results: CSF sCD25 levels in patients with primary HLH were higher than those in patients with Epstein-Barr virus infection-associated HLH, and the median level was 444 pg/ml. The difference in CSF sCD25 levels between the non-CNS group and the CNS group was statistically significant (591 [259-33,643] pg/ml vs. 123 (36-437) pg/ml, p < .001). The best cutoff value of CSF sCD25 was 273.5 pg/ml (AUC = 0.987, 95% CI: 0.972-1.000), with sensitivity, specificity, positive predictive values, and negative predictive values of 96.4%, 92.8%, 81.8%, and 98.7%, respectively. CSF sCD25 in the severe CNS involvement group was significantly higher than that in the nonsevere CNS involvement group (p = .014). The 3-year overall survival (OS) of patients with high CSF sCD25 levels was lower than that of patients with low CSF sCD25 levels(71.6% ± 8.1% vs. 93.3% ± 2.9%, hazard ratio [HR] = 3.637, p = .003).

Conclusion: Increased CSF sCD25 levels in active disease can predict CNS-HLH. Primary HLH has a higher CSF sCD25 level than Epstein-Barr virus infection-associated HLH. Patients who are diagnosed with CNS-HLH with CSF sCD25 levels higher than 273.5 pg/ml are more likely to develop severe CNS involvement, suggesting a poor prognosis.