Limited utility of the HScore in detecting secondary haemophagocytic lymphohistiocytosis in COVID-19: response.

We initially responded to the prior recommendations in the Lancet on screening with the HScore to guide immunosuppressive therapy in COVID‐19 patients. We identified that this is likely to be inappropriate due to the differences in the COVID‐19‐related hyperinflammatory syndrome versus other alternate causes of secondary haemophagocytic lymphohistiocytosis (sHLH). In this letter, Sangha et al. acknowledge that the HScore is not well suited to guide immunosuppressive therapy in COVID‐19 patients.

Patients with severe COVID‐19 do have a hyperinflammatory process, but it should not necessarily be regarded as sHLH — therefore the HLH 2004/HScore systems should not be used to determine treatment in this setting. We would contend that the decision on using dexamethasone and tocilizumab in severe COVID‐19 should not be based on whether the patient meets previously defined criteria for secondary HLH and especially not on the presence or absence of haemophagocytosis in the bone marrow. Haemophagocytosis in itself is neither sensitive nor specific; any benefit of a bone marrow biopsy in the context of COVID‐19 is more likely to come from ruling out other pathology. Additionally, bone marrow biopsies might introduce unnecessary delays in management and potential infective risk to operators/laboratory personnel who also deal with vulnerable haemato‐oncology patients. Finally, trying to categorise SARS‐CoV‐2‐related hyperinflammation according to old concepts is not necessarily a useful approach in the investigation and treatment of severe COVID‐19, which should follow the national guidelines and clinical trials.