**3. Results**

#### *3.1. Study Population*

As depicted in Figure 1, a total of 763 records from patients suspected with PBC was identified through an extended database search. Among them, 283 patients were excluded from this study, mainly due to subsequent incomplete data sets (150 patients), liver transplantation (124 patients) or lack of subsequent UDCA treatment (nine patients). Patients with apparent autoimmune hepatitis overlap were also excluded. Therefore, 480 patients with PBC were enrolled for first-line therapy analysis. A total of 116 patients showed an inadequate response to UDCA according to at least one criterion and were therefore included for second-line therapy analysis.

**Figure 1.** Study flow diagram. In total, 763 patients with confirmed PBC from 10 independent hepatological referral centers were screened for study eligibility and real-world first-line UDCA treatment regimens and subsequent response rates at 12 months after the initiation of treatment were evaluated in 480 patients. Patients with an inadequate response to at least one of the response criteria (*n* = 116) were evaluated for hitherto available second-line treatment regimens and subsequent response rates at 12 months after treatment modification.

#### *3.2. Baseline Characteristics*

The overall study population of 480 patients with PBC comprised 431 females (89.8%) and 49 (10.2%) males (Table S1). The median age at UDCA treatment initiation was 57 years (Q1– Q3: 48 to 64 years). In 83.5% (401/480) of the patients, the diagnosis of PBC was established based on cholestatic biochemical patterns and PBC-specific autoantibodies. In total, 399 (86.9%) patients out of 459 were AMA-positive. Autoantibodies against sp100 were determined in 112 patients, of which 28 (25%) had a positive result. A liver biopsy was carried out in 26.5% (127/480) and varied largely between the different centers (17.1 to 50%).
