RESUMEN
<p><b>OBJECTIVE</b>To explore etiologic fraction (EF) and interaction of serum hepatitis B surface antigen (HBsAg) carriage and other risk factors for primary hepatocellular carcinoma (PHC) in Wenzhou, Zhejiang, China.</p><p><b>METHODS</b>1:1 matched case-control study was carried out in Wenzhou, with 180 cases of PHC and 180 controls. EF and interactions of serum positive HBsAg [HBsAg(+)] and other risk factors for PHC were analyzed by Mantel-Haenszel stratified method and conditional multiple logistic regression.</p><p><b>RESULTS</b>Serum HBsAg(+), poor economic status during the past five years, preferring intake of pickled vegetables, history of PHC in their first-degree relatives, and negative life events all were risk factors for PHC, with EFs of 0.728, 0.245, 0.224, 0.084, and 0.234, respectively. There existed interactions of HBsAg(+) with other risk factors, including poor economic status during the past five years, preferring intake of pickled vegetables, history of PHC in their first-degree relatives, and negative life events, with etiologic fractions attributable to interaction [EF (A x B)] of 0.770, 0.630, 0.848, and 0.627, and indices of interaction of 0.789, 0.638, 0.852, and 0.634, respectively.</p><p><b>CONCLUSIONS</b>Main risk factor for PHC in Wenzhou, Zhejiang, China could include HBsAg(+), poor economic status during the past five years, preferring intake of pickled vegetables, history of PHC in their first-degree relatives, and negative life events. HBsAg(+) plus any of the following factors, such as poor economic status during the past five years, preferring intake of pickled vegetables, history of PHC in their first-degree relatives, and negative life events, could increase the risk of PHC.</p>