The Clinical Impact of Impaired Natural-Killer Cell Cytotoxicity for Diagnosis and Prognostication in Adult Patients with Febrile Cytopenia Including Hemophagocytic Lymphohistiocytosis and Similar Diseases: The Results of Prospective Phase II Observational Study

Abstract

Background: Hemophagocytic lymphohistiocytosis (HLH) is a severe systemic inflammatory disease which is life-threatening if not detected earlier and treated appropriately. The diagnosis of HLH is sometimes confused due to other similar febrile diseases with cytopenia such as severe infection, flare-up of autoimmune disease, and malignant conditions. Decreased natural-killer cell (NK) cytotoxicity is an important diagnostic parameter for HLH, but we do not know the level and role in similar febrile diseases.Aim: We tried to identify the different levels in variable febrile diseases and find out the role for diagnosis and prognostication in adult patients with HLH compared to other similar diseases.Methods: We prospectively enrolled 41 patients from 2015 to 2017. Adult patients older than 18 years with fever>38℃ presenting cytopenia in at least two lineages (neutrophil<1,000/㎕, platelet<100,000/㎕, Hemoglobin<9.0/dL) were included. Patients with previous hematological diseases were excluded. Diagnosis of HLH was based on HLH2004 criteria. Infection was managed according to the protocol and HLH-suspected patients were initially treated with 10mg/BSA of dexamethasone, and etoposide was considered if clinical improvement was not observed within 7 days after dexamethasone. Patients other than HLH were treated with disease-specified therapy. NK cytotoxicity was calculated at diagnosis by antibody-dependent Raji-cell cytotoxicity (ADCC) assay and K562-cell direct lysis using flow cytometry. Concomitantly, CD107a expression and NK-induced interferon gamma were also calculated.Results: HLH was diagnosed in 29 patients caused by viral infection (n=8), malignancies (n=6), autoimmune diseases (n=6), bacterial infection (n=2), malaria (n=1), and unidentified origin (n=6). Febrile diseases other than HLH (n=12) were diagnosed with hematological disease (n=7), infectious mononucleosis (n=2), SLE (n=2), Kikuchi disease (n=1). The results of both K562 lysis and ADCC assay were highly correlated but the diagnostic power was greater in ADCC assay. In the entire group, ADCC lower than 40% was related with poor 1-year OS (70.2% vs. 100%, P=0.062). Median ADCC level was lower in HLH (20.5% vs. 37.7%, P=0.045) and in HLH with poor dexamethasone response (12.0% vs. 30.7%, P=0.009). ROC curve revealed that ADCC lower than 22.8% was useful for diagnosis of HLH and lower than 12.8% was related with poor treatment response. Unfortunately, CD107a expression and NK-induced interferon gamma was not useful for diagnosis and prognostication.Conclusion: Lower NK cytotoxicity was diagnostic for HLH compared to other febrile disease with cytopenia, and we identified ADCC lower than 40% was related with poor OS and lower than 12.8% was predictable for severe HLH presenting poor treatment outcome. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.