Epidemiology of primary biliary cholangitis in Hong Kong and risk factors associated with adverse liver outcomes

Abstract

Background: There are few population-based studies on the epidemiology and outcomes of primary biliary cholangitis (PBC) in Asia. In addition, risk factors for adverse outcomes (defined as hepatocellular carcinoma [HCC], hepatic decompensation, liver transplantation or death) in Chinese PBC patients treated with ursodeoxycholic acid (UCDA) have not been well defined.

Objectives: This study aimed to determine the epidemiology of PBC in Hong Kong, and to investigate the risk factors for adverse outcomes

Methods: In the first part of the study, I retrieved data from the electronic database of Hong Kong Hospital Authority, which is the only public healthcare provider covering more than 80% of all hospital admissions. PBC cases from the year of 2000 to 2015 were identified with the International Classification of Diseases (ICD)-9 code of 571.6. I estimated the age/sex-adjusted incidence and prevalence of PBC, and analyzed the adverse outcomes.

In the second part of the study, I performed a retrospective cohort study of PBC patients who had follow-up in Queen Mary Hospital (QMH) between 2000 and 2015. Data of patient demographics, clinical, laboratory and histological parameters were retrieved from the electronic database and medical records. Cox proportional hazards model was used to identify variables associated with adverse outcomes in patients receiving UCDA. Suboptimal response to UCDA was defined by the Paris-1 criteria.

Results: A total of 1,016 PBC patients aged at least 20 years were identified (female-to-male ratio 4:1; median age at diagnosis 60.6 years, interquartile range [IQR] 51.8 to 72.6 years). By using the population in the year 2000 in Hong Kong as the reference population, the average annual age/sex-incidence rate was 8.4 per million person-years, and the average age/sex-adjusted prevalence was 56.4 per million. Age/sex-adjusted annual incidence rate of PBC increased from 6.7 to 8.1 per million person-years between 2000 and 2015 (Poisson p=0.002). Age/sex-adjusted prevalence of PBC increased from 31.1 to 82.3 per million (Poisson p<0.001). There were 50 new HCC cases (4.9% of total PBC cases; median age 73.5 years). Liver transplantation was performed in 49 patients (4.8% of total PBC cases; median age 54.0 years). The median life expectancy was 71.5 years (IQR 61.1 to 80.9 years). Case fatality risk decreased from 10.8% in 2000 to 5.4% in 2014 (Poisson p=0.001).

For the QMH patient cohort, 185 PBC cases were identified (94.4% received UCDA for at least one year), with a median follow-up duration of 7.6 years (IQR: 3.7 to 12 years). HCC developed in 14 patients (7.9%) and 61 patients (34.3%) died. The 5-year, 10-year and 15-year adverse outcome-free survival probabilities were 72.5%, 56.5% and 44.0%, respectively. Increasing age (hazard ratio [HR] 1.04), cirrhosis (HR 4.91) and suboptimal response to UCDA (HR 2.30) were independent risk factors for adverse outcomes.

Conclusions: This is the first population-based study of the epidemiology of PBC in Hong Kong. There is a considerable increase in both the incidence and prevalence of PBC, which is associated with significant morbidity and mortality. Independent risk factors for adverse outcomes included increasing age, cirrhosis and suboptimal response to UCDA.