Background  Locally acquired hepatitis E is an emerging infection in developed countries and can be misdiagnosed as drug-induced liver injury.

Aim  To study the role of hepatitis E virus (HEV) testing in drug-induced liver injury.

Methods  Retrospective review of a cohort of patients with suspected drug-induced liver injury (n = 69) and hepatitis E (n = 45). The standard criteria for drug-induced liver injury were applied. Patients with suspected drug-induced liver injury who met these criteria were retrospectively tested for HEV on stored sera taken at the time of presentation. The two cohorts were compared to determine variables that predicted either of the diagnoses.

Results  Forty-seven out of 69 patients had criterion-referenced drug-induced liver injury. 22/47 were HEV negative and thus had confirmed drug-induced liver injury. 19/47 were not tested for HEV, as there was no sera available from the time of presentation. 6/47 were HEV positive and thus did not have drug-induced liver injury, but had hepatitis E infection. Compared to patients with confirmed drug-induced liver injury, patients with hepatitis E were significantly more likely to be male (OR 3.09, CI 1.05–9.08); less likely to present in November and December (0.03, CI 0.01–0.52); have lower serum bilirubin (P = 0.015); and higher serum alanine aminotransferase (P < 0.001) and alanine aminotransferase/alkaline phosphatase ratio (P < 0.001).

Conclusion  The diagnosis of drug-induced liver injury is not secure without testing for HEV.