# Identifying Patients With Undiagnosed Haemophagocytic Lymphohistiocytosis: Is Ferritin a Useful Screening Tool?

## TL;DR

This study explores whether high ferritin levels can help identify patients with undiagnosed hemophagocytic lymphohistiocytosis, a rare but severe inflammatory condition.

## Contribution

The study proposes a potential screening tool for hemophagocytic lymphohistiocytosis using ferritin levels combined with clinical features like fever.

## Key findings

- 14 out of 120 patients had an HScore ≥169, indicating high likelihood of HLH.
- Ferritin >5,000 ug/L combined with fever was 100% sensitive for secondary HLH.
- Low clinician awareness and missing lab values may delay HLH diagnosis.

## Abstract

Background

Haemophagocytic lymphohistiocytosis (HLH) is an uncommon hyperinflammatory syndrome characterised by excessive cytotoxic T-cell and histiocyte activity, which can progress to cytokine storm and multi-organ failure. Left untreated, it has a high mortality, but is often diagnosed late or not at all.

Aim

This study aimed to identify patients with undiagnosed secondary HLH at the Newcastle Hospitals NHS Foundation Trust in Newcastle, England, and assess the usefulness of ferritin in developing a screening tool for early recognition of high-risk patients.

Methods

A retrospective analysis of all patients with serum ferritin of >5,000 ug/L was performed. Two established scoring systems for HLH were applied. Clinical features and laboratory values were evaluated, and statistical analysis was applied. Patients’ ages ranged from 19 to 90 years old.

Results

Of 120 patients included in the final analysis, 14 had an HScore of ≥169 (93% sensitive and 86% specific for HLH), of which six were diagnosed with HLH by clinicians.

Conclusion

Utilising the HScore, eight additional patients would have been diagnosed with HLH. Low awareness of HLH amongst clinicians and/or unavailability of key laboratory values may have prevented diagnosis. Ferritin may be a useful component of a screening tool for HLH, especially combined with other key features (fever and cytopaenias). The presence of fever and ferritin of >5,000 ug/L was 100% sensitive and 68.3% specific for sHLH in our study, potentially forming a base from which a screening tool or algorithm could be developed for clinical use.