Abstract: Objective To evaluate the diagnostic value of anti-filamentous actin antibodies (AFA) on patients
with autoimmune hepatitis type Ⅰ (AIH-Ⅰ). Methods The clinical data of 163 cases with AIH-Ⅰ, 5 cases with
AIH-Ⅱ, 26 cases with AIH-Ⅲ, 26 cases with primary biliary cirrhosis (PBC), 5 cases with primary sclerosing
cholangitis (PSC), 2 cases with autoimmune disease overlap syndrome (AIDOS), 95 cases with other liver diseases
and 197 blood donors (controls) were collected. AFA and anti-smooth muscle antibodies (ASMA) were evaluated
by ELISA and the results were analyzed. Results The positive rate of AFA and ASMA in patients with AIH-Ⅰ had
no statistically significant differences (χ 2 = 0.37, P = 0.54). The positive rates of ASMA in patients with AIH-Ⅲ and
hepatitis B were higher than those of AFA and the differences were statistically significant (χ 2 = 5.65, 6.37; P = 0.02,
0.01). The relevance ratio of AFA in AIH patients with ASMA ≥ 20 U/L was higher than 98.27%, the result
was closely correlated to the concentration of ASMA (r = 0.88, 95% CI: 0.66～0.99, P = 0.00). In prospective
analysis, AFA showed a similar sensitivity (71.78% vs 68.71%) but a superior specificity (83.87% vs 54.84%)
and a higher Youden index (0.56 vs 0.24) in patients with AIH-Ⅰ compared with ASMA. Conclusions The AFA
was a useful tool with a superior specificity and a higher Youden index in the diagnosis of AIH-Ⅰ compared
with ASMA.