A population-based study of hepatitis D virus as potential risk factor for hepatocellular carcinoma.

Hepatitis D virus (HDV) is dependent on the presence of hepatitis B virus (HBV) for transmission and replication because of its inability to produce its own coat. It remains unclear whether HDV infection increases the risk of hepatocellular carcinoma. Using the Swedish Hospital Discharge Register and Outpatient Registry, we identified 9160 patients with chronic HBV infection between 1997 and 2008, of whom 327 had chronic HDV infection and 323 had acute HDV infection. Standardized incidence ratios (SIRs) were calculated for these patients compared with the general population. The risk of hepatocellular carcinoma was greatly increased in patients with HBV and HDV (SIR = 137.17, 95% confidence interval [CI] = 62.19 to 261.51). The risk of hepatocellular carcinoma among patients with HBV and HDV was increased (SIR = 6.11, 95% CI = 2.77 to 11.65) when patients with chronic HBV infection alone were used as the reference population. Similar results were observed for patients with chronic HDV infection (SIR = 99.26, 95% CI = 42.39 to 196.55). Our findings indicate that HDV is a strong risk factor for hepatocellular carcinoma.