Prevalence and Diagnostic Challenge of Hemophagocytic Lymphohistiocytosis Syndrome in Critically Ill Patients.

backgroundHemophagocytic lymphohistiocytosis (HLH) is a rare hyperinflammatory syndrome. It is a severe condition with a challenging diagnosis in the intensive care unit (ICU), for which current recommendations rely on fulfilling five of eight HLH-2004 criteria.

methodsOur single-center retrospective cohort included adults admitted to the ICU in whom HLH was diagnosed, suspected, or excluded. The primary outcome was the prevalence of HLH in the ICU according to the HLH 2004 criteria. Additional factors analyzed included prognosis and diagnosis (determined by clinician judgment, HLH 2004 criteria with a four variable threshold and HScore).

resultsAmong 123 included patients, 30 met HLH-2004 criteria, corresponding to a prevalence of 0.42% of ICU admissions, likely underestimated. Their 28-day mortality rate was 46.7%; their 1-year mortality rate was 75%. In the entire cohort, absence of infection as a trigger and higher SAPS II scores were independently associated with 28-day mortality in multivariate analysis. Diagnostic concordance was 69.1% with the HScore, 61.8% with clinician judgment, and 71.5% with the four-variable HLH-2004 threshold, yielding an overall agreement of 46.3%.

conclusionOur study describes a population of adults suspected of HLH in the ICU. Improved diagnostic strategies are needed to facilitate timely recognition and optimize patient outcomes.