Hypomethylating agent monotherapy in core binding factor acute myeloid leukemia: a French multicentric retrospective study.

Very few data are available about hypomethylating agent (HMA) efficiency in core binding factor acute myeloid leukemias (CBF-AML). Our main objective was to evaluate the efficacy and safety of HMA in the specific subset of CBF-AML. Here, we report the results of a multicenter retrospective French study about efficacy of HMA monotherapy, used frontline or for R/R CBF-AML. Forty-nine patients were included, and received a median of 5 courses of azacitidine (n = 46) or decitabine (n = 3). ORR was 49% for the whole cohort with a median time to response of 112 days. After a median follow-up of 72.3 months, median OS for the total cohort was 10.6 months. In multivariate analysis, hematological relapse of CBF-AML at HMA initiation was significantly associated with a poorer OS (HR: 2.13; 95%CI: 1.04-4.36; p = 0.038). Responders had a significantly improved OS (1-year OS: 75%) compared to non-responders (1-year OS: 15.3%; p < 0.0001). Hematological improvement occurred for respectively 28%, 33% and 48% for patients who were red blood cell or platelet transfusion-dependent, or who experienced grade 3/4 neutropenia at HMA initiation. Adverse events were consistent with the known safety profile of HMA. Our study highlights that HMA is a well-tolerated therapeutic option with moderate clinical activity for R/R CBF-AML and for patients who cannot handle intensive chemotherapy.

[Mobilization and conditioning protocols actualization for autologous stem cell transplantation for autoimmune diseases: Guidelines from MATHEC-SFGM-TC]. / Actualisation des protocoles de mobilisation et conditionnement pour la pratique des autogreffes de cellules souches hématopoïétiques chez les patients atteints de maladies auto-immunes : recommandations de la Société francophone de greffe de moelle et de thérapie cellulaire (MATHEC-SFGM-TC).

The Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC) organized the 13th workshop on hematopoietic stem cell transplantation clinical practices harmonization procedures in September 2022 in Lille, France. The aim of this workshop is to update the mobilization and conditioning protocols for autologous hematopoietic stem cell transplantation for autoimmune diseases, and to specify contraindications for transplant, conditioning regimen selection, immunosuppressive treatment discontinuation before mobilization and disease-specific surveillance.

Frontal Intermittent Rhythmic Delta Activity Is a Useful Diagnostic Tool of Neurotoxicity After CAR T-Cell Infusion.

BACKGROUND AND OBJECTIVES: Chimeric antigen receptor (CAR) T-cell therapies have dramatically improved the prognosis of patients with relapsed or refractory hematologic malignancies; however, cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome (ICANS) occur in ∼100 and 50% of patients, respectively. This study aimed to determine whether EEG patterns may be considered as diagnostic tools for ICANS. METHODS: Patients who received CAR T-cell therapy at Montpellier University Hospital between September 2020 and July 2021 were prospectively enrolled. Neurologic signs/symptoms and laboratory parameters were monitored daily for 14 days after CAR T-cell infusion. EEG and brain MRI were performed between day 6 and 8 after CAR T-cell infusion. EEG was performed again on the day of ICANS occurrence, if outside this time window. All collected data were compared between patients with and without ICANS. RESULTS: Thirty-eight consecutive patients were enrolled (14 women; median age: 65 years, interquartile range: [55-74]). ICANS was observed in 17 of 38 patients (44%) after a median time of 6 days after CAR T-cell infusion (4-8). The median ICANS grade was 2 (1-3). Higher C-reactive protein peak (146 mg/L [86-256], p = 0.004) at day 4 (3-6), lower natremia (131 mmol/L [129-132], p = 0.005) at day 5 (3-6), and frontal intermittent rhythmic delta activity (FIRDA, p < 0.001) on EEG between days 6 and 8 after infusion were correlated with ICANS occurrence. FIRDA was only observed in patients with ICANS (N = 15/17, sensitivity of 88%) and disappeared after ICANS resolution, usually after steroid therapy. Except for hyponatremia, no other toxic/metabolic marker was associated with FIRDA (p = 0.002). The plasma concentration of copeptin, a surrogate marker of antidiuretic hormone secretion, assessed at day 7 after infusion, was significantly higher in patients with (N = 8) than without (N = 6) ICANS (p = 0.043). DISCUSSION: FIRDA is a reliable diagnostic tool for ICANS, with a sensitivity of 88% and a negative predictive value of 100%. Moreover, as this EEG pattern disappeared concomitantly with ICANS resolution, FIRDA could be used to monitor neurotoxicity. Finally, our study suggests a pathogenic pathway that starts with increased C-reactive protein, followed by hyponatremia and eventually ICANS and FIRDA. More studies are required to confirm our results. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that FIRDA on spot EEG accurately distinguishes patients with ICANS compared with those without after CAR T-cell therapy for hematologic malignancy.

Preventive plasmapheresis for rituximab related flare in cryoglobulinemic vasculitis.

Introduction: Rituximab monotherapy represents the main therapeutic option for cryoglobulinemic vasculitis (CV) with severe organ involvement. However, initial worsening of the CV, known as rituximab-associated CV flare (=CV flare), has been described and are associated with high mortality rates. The aim of the present study is to evaluate the outcomes of plasmapheresis initiated before or during rituximab treatment, as prevention of CV flare. Methods: We conducted a retrospecttive study in our tertiary referral center from 2001 to 2020. We have included all patients with CV receiving rituximab and divided them in two groups whether they had flare prevention by plasmapheresis or not. We evaluated rituximab-related CV flare incidence in both groups. CV flare was defined as the onset of a new organ involvement or worsening of the initial manifestations within 4 weeks following rituximab. Results: Among the 71 patients included, 44 received rituximab without plasmapheresis (control = CT cohort) and 27 received plasmapheresis before or during rituximab treatment (preventive plasmapheresis = PP cohort). PP was given to patients thought to have a high risk of CV flare, with significantly more severe diseases than patients in the CT cohort. Despite this, no CV flare was observed in the PP group. In the other hand, 5 flares occurred in the CT cohort. Conclusion: Our results show that plasmapheresis is efficient and well tolerated to prevent rituximab-associated CV flare. We believe that our data support the use of plasmapheresis in this indication, especially in patients with high risk of CV flare.

Sodium flux during hemodialysis and hemodiafiltration treatment of acute kidney injury: Effects of dialysate and infusate sodium concentration at 140 and 145 mmol/L.

BACKGROUND: A higher sodium (Na) dialysate concentration is recommended during renal replacement therapy (RRT) of acute kidney injury (AKI) to improve intradialytic hemodynamic tolerance, but it may lead to Na loading to the patient. We aimed to evaluate Na flux according to Na dialysate and infusate concentrations at 140 and 145 mmol/L during hemodialysis (HD) and hemodiafiltration (HDF). METHODS: Fourteen AKI patients that underwent consecutive HD or HDF sessions with Na dialysate/infusate at 140 and 145 mmol/L were included. Per-dialytic flux of Na was estimated using mean sodium logarithmic concentration including diffusive and convective influx. We compared the flux of sodium between HD140 and 145, and between HDF140 and 145. RESULTS: Nine HD140, ten HDF140, nine HD145, and 11 HDF145 sessions were analyzed. A Na gradient from the dialysate/replacement fluid to the patient was observed with dialysate/infusate Na at 145 mmol/L in both HD and HDF (p = 0.01). The comparison of HD145 to HD140 showed that higher Na dialysate induced a diffusive Na gradient to the patient (163 mmol vs. -25 mmol, p = 0.004) and that of HDF145 to -140 (211 vs. 36 mmol, p = 0.03) as well. Intradialytic hemodynamic tolerance was similar across all RRT sessions. CONCLUSIONS: During both HD and HDF, a substantial Na loading occurred with a Na dialysate and infusate at 145 mmol/L. This Na loading is smaller in HDF with Na dialysate and infusate concentration at 140 mmol/L and inversed with HD140. Clinical and intradialytic hemodynamic tolerance was fair regardless of Na dialysate and infusate.

[Management of neurotoxicity following CAR-T cell therapy: Recommendations of the SFGM-TC]. / Prise en charge du syndrome de neurotoxicité associée au traitement par cellules CAR-T chez l'adulte et l'enfant : recommandations de la SFGM-TC.

The immune effector cell-associated syndrome (ICANS) has been described as the second most frequent specific complication following CAR-T cell therapy. The median time to the onset of neurological symptoms is five days after CAR-T infusion. ICANS can be concomitant to cytokine release syndrome but often follows the resolution of the latter. However, 10 % of patients experience delayed onset after 3 weeks of CAR-T cell infusion. The duration of symptoms is usually short, around five days if an early appropriate treatment is given. Symptoms are heterogeneous, ranging from mild symptoms quickly reversible (alterations of consciousness, deterioration in handwriting) to more serious forms with seizures or even a coma. The ICANS severity is currently based on the ASTCT score. The diagnosis of ICANS is clinical but EEG, MRI and lumbar punction can help ruling out alternative diagnoses. The first line treatment consists of high-dose corticosteroids. During the twelfth edition of practice harmonization workshops of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC), a working group focused its work on updating the SFGM-TC recommendations on the management of ICANS. In this review we discuss the management of ICANS and other neurological toxicities in patients undergoing of CAR-T cell therapy. These recommendations apply to commercial CAR-T cells, in order to guide strategies for the management neurological complications associated with this new therapeutic approach.

[Management of cytokine release syndrome and macrophage activation syndrome following CAR-T cell therapy: Guidelines from the SFGM-TC]. / Prise en charge du syndrome de relargage cytokinique et du syndrome d'activation macrophagique après traitement par CAR-T cells : recommandations de la SFGM-TC.

The use of chimeric antigen receptor T cells (CAR-T) has increased since their approval in the treatment of several relapsed/refractory B cell malignancies. The management of their specific toxicities, such as cytokine release syndrome (CRS), tends to be better understood and well-defined. During the twelfth edition of practice harmonization workshops of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC), a working group focused its work on the management of patients developing CRS following CAR-T cell therapy. A special chapter has been allocated to macrophage activation syndrome (MAS), a rare but life-threatening complication post-CAR-T. In addition to symptomatic measures and preemptive broad-spectrum antibiotics, immunomodulators such as tocilizumab and corticosteroids remain the corner stone for the treatment of CRS. Tocilizumab/corticosteroids-resistant CRS associated with haemophagocytosis markers (spleen and liver enlargement, hyperferritinaemia>10,000ng/mL, hypofibrinogenemia…) should direct the diagnosis towards an overlapping CRS/MAS. An adapted treatment will be based on high-dose IV anakinra and corticosteroids and chemotherapy with etoposide at late refractory stages. These complications and others delignate the need of close collaboration with an intensive care unit.

Outcomes after allogeneic hematopoietic stem cell transplantation for adults with primary mediastinal B cell lymphoma: a SFGM-TC and LYSA study.

Background: Despite therapeutic progress, 10 to 30% of adult patients with primary mediastinal B cell lymphoma (PMBCL) are primary refractory or experience early relapse (R/R). Allogeneic stem cell transplantation (allo-HSCT) thus remains a potentially curative option in this setting.Material and Methods: In this multicenter retrospective study, the outcomes of 33 French and Belgian adult patients allo-transplanted for R/R PMBCL between January 1999 and December 2018, were examined.Results: At allo-HSCT time, patients had received a median of 3 treatment lines, 50% of them were in complete response, 40% in partial response and 10% had a progressive disease. Forty-two percent of the donors were siblings and 39% matched related. The median follow-up for alive patients was 78 months (3.5-157). Considering the whole cohort, 2-year overall survival (OS), progression free survival (PFS) and graft-versus-host disease-free/relapse-free survival (GRFS) were 48% (95%CI: 33-70), 47% (95%CI: 33-68) and 38.5% (95%CI: 25-60) respectively. Cumulative incidence of relapse and non-relapse mortality rates were respectively 34% (95%CI: 18-50) and 18% (95%CI: 7-34). Disease status at transplant was the only factor predicting survivals, patients with progressive disease showing significant lower 2-year PFS (HR: 6.12, 95%CI: 1.32-28.31, p = 0.02) and OS (HR: 7.04, 95%CI: 1.52-32.75, p = 0.013). A plateau was observed for OS and PFS after 4 years with 10 patients alive after this date, suggesting that almost one third of the patients effectively salvaged and undergoing allo-SCT could be cured.Conclusion: This study indicates that allo-HSCT is a valid therapeutic option for R/R PMBCL, providing durable remissions.

A real-world comparison of tisagenlecleucel and axicabtagene ciloleucel CAR T cells in relapsed or refractory diffuse large B cell lymphoma.

Axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel) have both demonstrated impressive clinical activity in relapsed/refractory (R/R) diffuse large B cell lymphoma (DLBCL). In this study, we analyzed the outcome of 809 patients with R/R DLBCL after two or more previous lines of treatment who had a commercial chimeric antigen receptor (CAR) T cells order for axi-cel or tisa-cel and were registered in the retrospective French DESCAR-T registry study ( NCT04328298 ). After 1:1 propensity score matching (n = 418), the best overall response rate/complete response rate (ORR/CRR) was 80%/60% versus 66%/42% for patients treated with axi-cel compared to tisa-cel, respectively (P < 0.001 for both ORR and CRR comparisons). After a median follow-up of 11.7 months, the 1-year progression-free survival was 46.6% for axi-cel and 33.2% for tisa-cel (hazard ratio (HR) = 0.61; 95% confidence interval (CI), 0.46-0.79; P = 0.0003). Overall survival (OS) was also significantly improved after axi-cel infusion compared to after tisa-cel infusion (1-year OS 63.5% versus 48.8%; HR = 0.63; 95% CI, 0.45-0.88; P = 0.0072). Similar findings were observed using the inverse probability of treatment weighting statistical approach. Grade 1-2 cytokine release syndrome was significantly more frequent with axi-cel than with tisa-cel, but no significant difference was observed for grade ≥3. Regarding immune effector cell-associated neurotoxicity syndrome (ICANS), both grade 1-2 and grade ≥3 ICANS were significantly more frequent with axi-cel than with tisa-cel. In conclusion, our matched comparison study supports a higher efficacy and also a higher toxicity of axi-cel compared to tisa-cel in the third or more treatment line for R/R DLBCL.

Outcomes of patients with aggressive B-cell lymphoma after failure of anti-CD19 CAR T-cell therapy: a DESCAR-T analysis.

Anti-CD19 chimeric antigen receptor (CAR) T-cells represent a major advance in the treatment of relapsed/refractory aggressive B-cell lymphomas. However, a significant number of patients experience failure. Among 550 patients registered in the French registry DESCAR-T, 238 (43.3%) experienced progression/relapse, with a median follow-up of 7.9 months. At registration, 57.0% of patients presented an age-adjusted International Prognostic Index of 2 to 3, 18.9% had Eastern Cooperative Oncology Group performance status ≥2, 57.1% received >3 lines of treatment prior to receiving CAR T-cells, and 87.8% received bridging therapy. At infusion, 66% of patients presented progressive disease, and 38.9% had high lactate dehydrogenase (LDH). Failure after CAR T-cell treatment occurred after a median of 2.7 months (range: 0.2-21.5). Fifty-four patients (22.7%) presented very early failure (day [D] 0-D30); 102 (42.9%) had early failure (D31-D90), and 82 (34.5%) had late (>D90) failure. After failure, 154 patients (64%) received salvage treatment: 38.3% received lenalidomide, 7.1% bispecific antibodies, 21.4% targeted treatment, 11% radiotherapy, and 20% immunochemotherapy with various regimens. Median progression-free survival was 2.8 months, and median overall survival (OS) was 5.2 months. Median OS for patients failing during D0-D30 vs after D30 was 1.7 vs 3.0 months, respectively (P = .0001). Overall, 47.9% of patients were alive at 6 months, but only 18.9% were alive after very early failure. In multivariate analysis, predictors of OS were high LDH at infusion, time to CAR-T failure

[Prevention and management of infections in patients undergoing CAR T-cell therapy: Recommendations of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]. / Prise en charge prophylactique, thérapeutique des complications infectieuses et vaccination des patients traités par CAR-T cells : recommandations de la Société francophone de greffe de moelle et de thérapie cellulaire (SFGM-TC).

Infections occurring after CAR T-cells are a common complication. At the acute phase of treatment following CAR T-cell infusion, the exact incidence of infections is unknown given the overlapping symptoms with cytokine release syndrome. The risk factors for infection include the malignant underlying disease and its multiple treatments, and an immunosuppressive state induced by CAR-T cells themselves and the treatment of their complications. During the twelfth edition of practice harmonization workshops of the Francophone society of bone marrow transplantation and cellular therapy (SFGM-TC), a working group focused its work on the management of post-CAR infectious complications. In this review we discuss anti-infection prophylaxis and vaccination of patients undergoing CAR T-cell therapy as well as a special chapter for the specific case of COVID-19. These recommendations apply to commercial CAR-T cells, in order to guide strategies for the management and prevention of infectious complications associated with this new therapeutic approach.

[Complications other than infections, CRS and ICANS following CAR T-cells therapy: Recommendations of the Francophone Society of bone marrow transplantation and cell therapy (SFGM-TC)]. / Complications des cellules CAR-T autres que les infections, CRS et ICANS : recommandations de la Société francophone de greffe de moelle et de thérapie cellulaire (SFGM-TC).

CAR-T cells are an innovative treatment for an increasing number of patients, particularly since the extension of their indication to mantle lymphoma and multiple myeloma. Several complications of CAR T-cell therapy, that were first described as exceptional, have now been reported in series of patients, since its first clinical use in 2011. Among them, cardiac complications, delayed cytopenias, acute and chronic Graft versus Host Disease, and tumoral lysis syndrome are recognized as specific potent complications following CAR T-cells infusion. During the twelfth edition of practice harmonization workshops of the Francophone society of bone marrow transplantation and cellular therapy (SFGM-TC), a working group focused its work on the management of these complications with focuses the epidemiology, the physiopathology and the risk factors of these 4 side effects. Our recommendations apply to commercial CAR-T cells, in order to guide strategies for the management of complications associated with this new therapeutic approach.

Clinical and Product Features Associated with Outcome of DLBCL Patients to CD19-Targeted CAR T-Cell Therapy.

CD19-directed CAR T-cells have been remarkably successful in treating patients with relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) and transformed follicular lymphoma (t-FL). In this cohort study, we treated 60 patients with axicabtagene ciloleucel or tisagenlecleucel. Complete and partial metabolic responses (CMR/PMR) were obtained in 40% and 23% of patients, respectively. After 6.9 months of median follow-up, median progression-free survival (mPFS) and overall survival (mOS) were estimated at 3.1 and 12.3 months, respectively. Statistical analyses revealed that CMR, PFS, and OS were all significantly associated with age-adjusted international prognostic index (aaIPI, p < 0.05). T-cell subset phenotypes in the apheresis product tended to correlate with PFS. Within the final product, increased percentages of both CD4 and CD8 CAR+ effector memory cells (p = 0.02 and 0.01) were significantly associated with CMR. Furthermore, higher CMR/PMR rates were observed in patients with a higher maximal in vivo expansion of CAR T-cells (p = 0.05) and lower expression of the LAG3 and Tim3 markers of exhaustion phenotype (p = 0.01 and p = 0.04). Thus, we find that aaIPI at the time of infusion, phenotype of the CAR T product, in vivo CAR T-cell expansion, and low levels of LAG3/Tim3 are associated with the efficacy of CAR T-cell therapy in DLBCL patients.

Coagulation disorders in patients with severe hemophagocytic lymphohistiocytosis.

BACKGROUND: Coagulation disorders are common in patients with hemophagocytic lymphohistiocytosis (HLH), associated with an increased risk of bleeding and death. We aim to investigate coagulation disorders and their outcome implications in critically ill patients with HLH. METHODS: We prospectively evaluated 47 critically ill patients with HLH (median age of 54 years [42-67]) between April 2015 and December 2018. Coagulation assessments were performed at day 1. Abnormal standard coagulation was defined as prothrombin time (PT) <50% and/or fibrinogen <2g/L. HLH aetiology was mostly ascribed to haematological malignancies (74% of patients). RESULTS: Coagulation disorders and severe bleeding events were frequent, occurring in 30 (64%) and 11 (23%) patients respectively. At day 1, median fibrinogen level was 2∙65g/L [1.61-5.66]. Fibrinolytic activity was high as suggested by increased median levels of D-dimers, fibrin monomers, PAI-1 (plasminogen activator inhibitor) and tPA (tissue plasminogen activator). Forty-one (91%) patients had a decreased ADAMTS13 activity (A Disintegrin-like And Metalloproteinase with ThromboSpondin type 1 repeats, member 13). By multivariable analysis, the occurrence of a severe bleeding (OR 3.215 [1.194-8.653], p = 0∙021) and SOFA score (Sepsis-Related Organ Failure Assessment) at day 1 (OR 1.305 per point [1.146-1.485], p<0∙001) were independently associated with hospital mortality. No early biological marker was associated with severe bleeding. CONCLUSIONS: Hyperfibrinolysis may be the primary mechanism responsible for hypofibrinogenemia and may also participate in ADAMTS13 degradation. Targeting the plasmin system appears as a promising approach in severe HLH-related coagulation disorders.

Infectious events in patients with severe COVID-19: results of a cohort of patients with high prevalence of underlying immune defect.

BACKGROUND: Empirical antibiotic has been considered in severe COVID-19 although little data are available regarding concomitant infections. This study aims to assess the frequency of infections, community and hospital-acquired infections, and risk factors for infections and mortality during severe COVID-19. METHODS: Retrospective single-center study including consecutive patients admitted to the intensive care unit (ICU) for severe COVID-19. Competing-risk analyses were used to assess cumulative risk of infections. Time-dependent Cox and fine and gray models were used to assess risk factors for infections and mortality. Propensity score matching was performed to estimate the effect of dexamethasone. RESULTS: We included 100 patients including 34 patients with underlying malignancies or organ transplantation. First infectious event was bacterial for 35 patients, and fungal for one. Cumulative incidence of infectious events was 27% [18-35] at 10 ICU-days. Prevalence of community-acquired infections was 7% [2.8-13.9]. Incidence density of hospital-acquired infections was 125 [91-200] events per 1000 ICU-days. Risk factors independently associated with hospital-acquired infections included MV. Patient's severity and underlying malignancy were associated with mortality. Dexamethasone was associated with increased infections (36% [20-53] vs. 12% [4-20] cumulative incidence at day-10; p = 0.01). After matching, dexamethasone was associated with hospital-acquired infections (35% [18-52] vs. 13% [1-25] at 10 days, respectively, p = 0.03), except in the subset of patients requiring MV, and had no influence on mortality. CONCLUSIONS: In this population of COVID-19 patients with high prevalence of underlying immune defect, a high risk of infections was noted. MV and use of steroids were independently associated with infection rate.

Impact of prone position in non-intubated spontaneously breathing patients admitted to the ICU for severe acute respiratory failure due to COVID-19.

PURPOSE: Studies performed in spontaneously breathing patients with mild to moderate respiratory failure suggested that prone position (PP) in COVID-19 could be beneficial. MATERIALS AND METHODS: Consecutive critically ill patients with COVID-19 were enrolled in four ICUs. PP sessions lasted at least 3 h each and were performed twice daily. A Cox proportional hazard model identified factors associated with the need of intubation. A propensity score overlap weighting analysis was performed to assess the association between spontaneous breathing PP (SBPP) and intubation. RESULTS: Among 379 patients, 40 underwent SBPP. Oxygenation was achieved by high flow nasal canula in all but three patients. Duration of proning was 2.5 [1.6;3.4] days. SBPP was well tolerated hemodynamically, increased PaO2/FiO2 (78 [68;96] versus 63 [53;77] mm Hg, p = 0.004) and PaCO2 (38 [34;43] versus 35 [32;38] mm Hg, p = 0.005). Neither day-28 survival (HR 0.51, 95% CI 0.16-1.16] nor risk of invasive ventilation [sHR 0.96; 95% CI 0.49;1.88] differed between patients who underwent PP and others. CONCLUSIONS: SBPP in COVID-19 is feasible and well tolerated in severely hypoxemic patients. It did not induce any effect on risk of intubation and day-28 mortality.

Diagnostic strategy for trigger identification in severe reactive hemophagocytic lymphohistiocytosis: A diagnostic accuracy study.

Reactive hemophagocytic lymphohistiocytosis (rHLH) management requires early recognition, trigger identification, and adequate treatment in order to reduce mortality. We assessed the diagnostic yield of tissue biopsies to identify trigger in severe rHLH. We included all consecutive patients presenting an rHLH diagnosis (HLH-2004 criteria) admitted to the intensive care unit (ICU) of a tertiary hospital. This retrospective diagnostic accuracy study was conducted according to the Standards for Reporting Diagnostic Accuracy Statement. Among the 134 included patients (median age 47 years [IQR 47-56]), an underlying immunodeficiency was previously known in 61.2%. rHLH trigger was identified in 127 patients (94.8%) (hematological disorder 75%, infection 16%, systemic disease 4%). Diagnostic yield of tissue biopsies was as follows: lymph node 75% (95% confidence interval [CI], 61-85), skin 50% (95% CI, 27-73), bone marrow 44% (95% CI, 34-55), liver 30% (95% CI, 15-49). Splenectomy (yield 77%; 95% CI, 46-95) was reserved to cases of diagnostic deadlock. Procedural severe adverse events included two cases of reversible hemorrhagic shock. Seventy-eight percent of patients received etoposide regarding to the rHLH severity, and 68% could receive trigger-specific treatment in the ICU. A comprehensive diagnostic workup led to an rHLH trigger identification in 95% of patients, allowing prompt initiation of appropriate therapy. Prospective studies to validate a standardized diagnostic approach are warranted.