False-negative rate of abdominal sonography for detecting hepatocellular carcinoma in patients with hepatitis B and elevated serum alpha-fetoprotein levels

Abstract

Objective: Routine screening for hepatocellular carcinoma among chronic carriers of hepatitis B virus using a combination of abdominal sonography and serum alpha-fetoprotein levels is widely practiced. Negative results on an abdominal sonogram generally indicate the absence of hepatocellular carcinoma despite the elevation of alpha-fetoprotein levels, but the false-negative rate of abdominal sonography has not been established prospectively.

Subjects and methods: In our screening program, we routinely investigated patients with Lipiodol (iodized oil) CT when they presented with alpha-fetoprotein levels above 20 ng/mL or a focal lesion as depicted on abdominal sonography. Lipiodol CT comprised a hepatic angiogram with injection of Lipiodol selectively in the hepatic arteries, followed by an unenhanced CT scan 10 days later. Positive findings on Lipiodol CT were confirmed histologically by biopsy or surgical resection. We defined false-negative as histologic diagnosis of hepatocellular carcinoma within 3 months of normal findings on screening abdominal sonography.

Results: One hundred three patients with elevated alpha-fetoprotein levels were investigated with Lipiodol CT within 2 months of abdominal sonography. Of these, three of 70 patients with negative abdominal sonography had histologically confirmed hepatocellular carcinoma. Thus, abdominal sonography has a false-negative rate of 4.3%. Lipiodol CT is associated with a significant false-positive rate of 43.7%. The sensitivity, specificity, and positive predictive value of abdominal sonography for early detection of hepatocellular carcinoma among hepatitis B virus carriers with elevated alpha-fetoprotein levels was 85.7%, 81.7%, and 54.5%, respectively.

Conclusion: Negative results on a screening abdominal sonogram among hepatitis B virus carriers with elevated alpha-fetoprotein levels does not rule out the presence of small hepatocellular carcinoma. Routine use of Lipiodol CT as a supplementary screening tool is not recommended.