A prospective study on the prevalence and clinical significance of autoantibodies in patients with suspected nonalcoholic fatty liver disease

BACKGROUND/AIMS: Exclusion of liver disease from other causes such as autoimmune hepatitis is necessary for diagnosis of nonalcoholic fatty liver disease (NAFLD). However, there has been no study on the prevalence and significance of autoantibodies in the patients with clinically suspected NAFLD in Korea, where hepatitis B is endemic and autoimmune hepatitis is relatively uncommon. METHODS: We prospectively tested for anti-nuclear antibody (ANA), anti-smooth muscle antibody (ASMA), and anti-mitochondrial antibody (AMA) in 135 serially enrolled patients with suspected NAFLD. We compared the clinical characteristics and biochemical indices of the ANA-positive or ASMA-positive group with those of the autoantibody-negative group. RESULTS: Sixteen patients (11.8%) had serum autoantibodies; there was ANA in 8 patients (5.9%), ASMA in 7 (5.1%), and AMA in 2 (1.5%). Both ANA and AMA were positive in one patient. The ANA-positive or ASMA-positive group showed an older age (49.5+/-13.0 vs. 42.0+/-10.9 years, respectively, P=0.018) and higher levels of serum globulin (3.1+/-0.4 vs. 2.9+/-0.4 g/dL, respectively, P=0.037), compared with the autoantibody-negative group. Two cases with positive ANA or ASMA fulfilled the diagnostic criteria for probable autoimmune hepatitis and two cases with positive AMA were suspected as primary biliary cirrhosis. CONCLUSIONS: These findings suggest that autoantibodies could be found in some patients with suspected NAFLD in Korea, AMA-positivity or ASMA-positivity could be associated with old age and high serum globulin, and some of the autoantibody-positive cases could be diagnosed as autoimmune hepatitis or primary biliary cirrhosis. Further studies are necessary to clarify the clinical significance of autoantibody positivity in those patients.