Low incidence and prevalence of primary biliary cirrhosis in Canterbury, New Zealand: a population-based study.

Abstract

Epidemiological data on primary biliary cirrhosis (PBC) in the Southern Hemisphere is scarce. Our aim was to perform a population-based epidemiological study of PBC in Canterbury, New Zealand. Multiple case-finding methods were employed. All public and private, adult and pediatric outpatient clinics, hospital discharge summaries, and laboratory and pathology reports were searched to identify all cases in the region. Cases were included if at least two of the following criteria were fulfilled: (1) positive anti-mitochondrial antibodies, (2) elevated alkaline phosphatase for greater than 6months, and (3) compatible liver histology. A total of 71 cases of PBC were included. The incidence in 2008 was 0.8 (95% confidence interval (CI) 0.1-1.6) per 100,000. The point prevalence on December 31, 2008 was 9.9 (95% CI 7.1-12.7) per 100,000. Male to female ratio was 1:11. At presentation, 45% were asymptomatic. Age at diagnosis peaked at the seventh decade with mean age at diagnosis of 61 (95% CI 58-64). This is the first population-based epidemiological study of PBC conducted in New Zealand and only the second in the Southern Hemisphere. The incidence and prevalence are lower than the Northern Hemisphere, even though the majority of our population has shared genetic background with some of these countries. Our study has provided further support to the hypothesis that there may be a protective effect or lack of a risk factor for PBC in New Zealand.