Value of hemophagocytosis in the diagnosis of hemophagocytic lymphohistiocytosis in critically ill patients

BackgroundFerritin is an established biomarker in the diagnosis of secondary hemophagocytic lymphohistiocytosis (HLH), which is diagnosed by the HLH-2004 criteria. Among these criteria, detection of hemophagocytosis through invasive procedures may delay early life saving treatment. Our aim was to investigate the value of hemophagocytosis in diagnosing HLH in critically ill patients.MethodsIn this secondary analysis of a retrospective observational study, we included all patients aged >= 18 years and admitted to any adult ICU at Charite-Universitatsmedizin Berlin between January 2006 and August 2018, who had hyperferritinemia (>= 500 mu g/L) and underwent bone marrow biopsy during their ICU course.ResultsTwo hundred fifty-two patients were included, of whom 31 (12.3%) showed hemophagocytosis. In multivariable logistic regression analysis, maximum ferritin was independently associated with hemophagocytosis. By removing hemophagocytosis from HLH-2004 criteria and HScore, prediction accuracy for HLH diagnosis was only marginally decreased compared to the original scores.ConclusionsOur results strengthen the diagnostic value of ferritin and underline the importance of considering HLH diagnosis in patients with high ferritin but only four fulfilled HLH-2004 criteria, when hemophagocytosis was not assessed or not detectable. Proof of hemophagocytosis is not required for a reliable HLH diagnosis.