JMIR Publications

ABSTRACT

Objective:

To compare different approaches to using the electronic health record (EHR) to build a cohort of Hemophagocytic Lymphohistiocytosis (HLH) patients, and to evaluate characteristics and outcomes of patients meeting the HLH-2004 diagnostic criteria who received HLH-directed therapies to those who did not.

Methods:

Three approaches to cohort development in the EHR were taken by identifying patients with: (1) an HLH-specific ICD-10 code, (2) an HLH-specific treatment plan, and (3) meeting the HLH-2004 clinical criteria for diagnosis of HLH. Among patients who met the HLH-2004 criteria, we evaluated the characteristics and outcomes of patients who received HLH-directed therapies to those who did not. HLH treatment was defined as either any chemotherapy, or HLH-specific therapy (dexamethasone, methylprednisolone, anakira, ruxolitinib, cyclosporine, etoposide or emapalumab).

Results:

We identified 388 patients with possible HLH across the three cohorts. An HLH ICD-10 diagnosis (n=220) and meeting five or more clinical criteria (n=245) were much more common than a HLH treatment plan (n=42). Among the patients meeting HLH-2004 clinical criteria, 193 (79%) received HLH-directed therapy. There was no difference in any specific HLH criteria between those who did and did not receive HLH-directed therapy. In-hospital mortality was very high among both groups and was 15.0% among those who received HLH-directed therapy and 13.5% among those who did not receive HLH-directed therapy. Among 1325 patients with an elevated ferritin and fever, only 252 (19%) met >5 clinical criteria.

Conclusions:

Constructing HLH cohorts from EHR data is challenging, with diagnosis codes, treatment plans, and clinical criteria each capturing distinct but overlapping populations.