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Abstract: Medical diagnosis and therapy often rely on laboratory testing. We observed mistaken testing in evaluations for hemophagocytic lymphohistiocytosis (HLH) that led to delays and adverse outcomes. Physicians were mistakenly ordering interleukin-2 and quantitative natural killer cell flow cytometry, rather than soluble interleukin 2 receptor (sIL2R) or qualitative natural killer functional tests in the evaluation of patients suspected to have HLH.We initiated a prospective quality improvement project to reduce mistaken testing, reduce delays in correct testing due to mistaken ordering, and improve HLH evaluations. This consisted of provider education, developing an evaluation algorithm, and ultimately required systems interventions such as pop-ups and removal of the mistaken tests from the electronic ordering catalog.Active education reduced mistaken testing significantly in HLH evaluations from baseline (73.3% vs 33.3%, P = .003, relative risk reduction (RRR) 54.5%), but failed to meet the pre-specified RRR cutoff for success (70%). Education alone did not significantly reduce the proportion of HLH evaluations with delays in sIL2R testing (23.3% vs 7.4%, P = .096). Mistaken testing increased after the active intervention ended (33.3% vs 43.5%, P = .390, with RRR 40.7% from baseline. Mistaken test removal was successful: mistaken testing dropped to 0% (P < .001, RRR 100%), saved $14,235 yearly, eliminated delays in sIL2R testing from mistaken testing (23.3% vs 0%, P = .008), and expedited sIL2R testing after admission for HLH symptoms (14.6 days vs 3.8 days, P = .0012). These data show systems controls are highly effective in quality improvement while education has moderate efficacy., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.)

Hemophagocytic lymphohistiocytosis (HLH) is a highly fatal, hyperinflammatory syndrome in adults triggered by an underlying illness in most cases. As such, suspicion of HLH dictates further investigation to identify the HLH trigger and determine treatment. HLH is clinically challenging due to diverse presentations and underlying triggers, provider unfamiliarity, and bleeding complications. Clinically, we observed diagnostic error from incorrect testing and cognitive biases (interleukin-2 confused with soluble interleukin-2 receptor and natural killer cell quantification confused with functional assays).This study reports our single institutional experience with adult HLH with the aim to reduce erroneous testing with a quality improvement (QI) project, and to facilitate trigger discovery and mitigate hemorrhage. Provider education on HLH testing was the prospective intervention, followed by mistaken test removal. HLH triggers and diagnostic utility were determined by retrospective chart review. Risk factors for hemorrhage were determined by multivariable analysis.Erroneous HLH testing was reduced from 74% to 24% of patients (P < .001) by the QI intervention. These changes were projected to save $11,700 yearly. The majority (64%) of patients evaluated for HLH were on non-hematology/oncology services, highlighting the need for vigilance in hematology consultation. Sixty-three patients met classic HLH-2004 criteria for HLH. Malignancy (38%), infection (27%), Epstein-Barr virus (EBV) (14%), or autoimmune disease (8%) triggered most HLH cases. HLH triggers were most commonly identified by serologic testing (27%) and bone marrow biopsy (19%). Biopsy of other affected organs based on PET-CT imaging after unsuccessful initial diagnostic measures was helpful, and focal fluorodeoxyglucose uptake was predictive of an underlying malignancy (likelihood ratio 8.3, P = .004). Major hemorrhage occurred in 41% of patients. On multivariable analysis the odds ratios (OR) for major hemorrhage were increased for patients with intensive care unit level care (OR 10.47, P = .005), and disseminated intravascular coagulation in the first week of admission (OR 10.53, P = .04).These data are incorporated into a framework to encourage early HLH recognition with the HScore, facilitate trigger identification, identify those at risk for hemorrhage, and minimize low-yield or erroneous testing.