Soluble CD25 (sCD25) in the Diagnosis and Management of Adult Hemophagocytic Lymphohistiocytosis
Diagnostic Criteria
- sCD25 ≥ 2400 U/mL is one of the eight HLH‑2004 diagnostic criteria; five of eight criteria are required for a definitive HLH diagnosis (Histiocyte Society HLH‑2004 guidelines) 1.
Diagnostic Performance
- sCD25 outperforms ferritin as a diagnostic test for adult HLH: area under the ROC curve = 0.90 (95 % CI 0.83‑0.97) versus ferritin AUC = 0.78 (95 % CI 0.67‑0.88). This finding comes from a diagnostic accuracy study in adults with suspected HLH. 1
- sCD25 is considered a “good to excellent” low‑cost diagnostic marker for adult HLH and should be obtained in all patients with suspected disease (expert consensus based on the same diagnostic study). 1
Laboratory Profile Context
- Elevated sCD25 accompanies a characteristic HLH laboratory pattern that includes high ferritin, triglycerides, transaminases, lactate dehydrogenase, and D‑dimer, together with low fibrinogen, albumin, and sodium. (Observational cohort) 2, 3
Clinical Interpretation
- Treatment should not be delayed while awaiting sCD25 results when clinical suspicion is high; HLH‑directed therapy may be started even if fewer than five criteria are met, provided the overall picture is compelling. (Guideline recommendation) 1
- sCD25 elevation reflects excessive activation of cytotoxic T‑cells, NK cells, and macrophages, the core pathophysiologic driver of HLH. (Pathophysiology review) 2
Treatment Recommendations
- The primary therapeutic approach follows the HLH‑2004 protocol, which combines dexamethasone, etoposide, and cyclosporine A and targets both hyperinflammation and the underlying trigger. (Guideline recommendation) 1
- Trigger identification is mandatory; screening should include malignancy (prevalence rises to ~68 % in adults > 60 y), viral infections (especially EBV and CMV), and autoimmune disorders. (Epidemiologic data) 2
Monitoring
| Parameter | Rationale | Evidence |
|---|---|---|
| sCD25 (serial) | Mirrors disease activity; decreasing levels indicate response to therapy. | Blood 2019 diagnostic/monitoring study [1] |
| Ferritin (serial) | Rapidly rises with active HLH but normalizes slowly; best used together with sCD25. | Praxis Medical Insights 2026 (clinical practice summary) [4] |
| Platelet count (q12‑24 h) | Platelet drops signal flares; should be tracked alongside temperature, spleen size, and liver enzymes. | Praxis Medical Insights 2026 (clinical practice summary) [4] |
Diagnostic Pitfalls
- HLH can mimic sepsis or multiple‑organ‑dysfunction syndrome; clinicians must maintain a high index of suspicion in critically ill patients with unexplained hyperinflammation. (Clinical warning) 4
- Absence of hemophagocytosis on initial bone‑marrow aspirate does not exclude HLH; repeat marrow sampling or examination of other tissues is advised when suspicion persists. (Guideline caution) 1, 4
- The HLH‑2004 criteria were originally derived for pediatric patients and have not been formally validated in adults, yet they remain the standard diagnostic framework, requiring clinical judgment. (Guideline commentary) 1