Clinical significance of cerebrospinal fluid soluble CD25 in pediatric hemophagocytic lymphohistiocytosis with central nervous system involvement

Abstract 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.