A novel approach to genome-wide association analysis identifies genetic associations with primary biliary cholangitis and primary sclerosing cholangitis in Polish patients.

BACKGROUND: Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are forms of hepatic autoimmunity, and risk for both diseases has a strong genetic component. This study aimed to define the genetic architecture of PBC and PSC within the Polish population. METHODS: Subjects were 443 women with PBC, 120 patients with PSC, and 934 healthy controls recruited from Gastroenterology Departments in various Polish hospitals. Allelotyping employed a pooled-DNA sample-based genome-wide association study (GWAS) approach, using Illumina Human Omni2.5-Exome BeadChips and the following novel selection criteria for risk loci: blocks of at least 10 single nucleotide polymorphisms (SNPs) in strong linkage disequilibrium, where the distance between each adjacent SNP pair in the block was less than 30 kb, and each SNP was associated with disease at a significance level of P < 0.005. A selected index SNP from each block was validated using TaqMan SNP genotyping assays. RESULTS: Nineteen and twenty-one SNPs were verified as associated with PBC and PSC, respectively, by individual genotyping; 19 (10/9, PBC/PSC) SNPs reached a stringent (corrected) significance threshold and a further 21 (9/12, PBC/PSC) reached a nominal level of significance (P < 0.05 with odds ratio (OR) > 1.2 or < 0.83), providing suggestive evidence of association. The SNPs mapped to seven (1p31.3, 3q13, 6p21, 7q32.1, 11q23.3, 17q12, 19q13.33) and one (6p21) chromosome region previously associated with PBC and PSC, respectively. The SNP, rs35730843, mapping to the POLR2G gene promoter (P = 1.2 × 10-5, OR = 0.39) demonstrated the highest effect size, and was protective for PBC, whereas for PSC respective SNPs were: rs13191240 in the intron of ADGRB3 gene (P = 0.0095, OR = 0.2) and rs3822659 (P = 0.0051, OR = 0.236) along with rs9686714 (P = 0.00077, OR = 0.2), both located in the WWC1 gene. CONCLUSIONS: Our cost-effective GWAS approach followed by individual genotyping confirmed several previously identified associations and discovered new susceptibility loci associated with PBC and/or PSC in Polish patients. However, further functional studies are warranted to understand the roles of these newly identified variants in the development of the two disorders.

Laboratory-based scoring system for prediction of hepatic inflammatory activity in patients with autoimmune hepatitis.

BACKGROUND & AIMS: In autoimmune hepatitis (AIH), inflammation is closely related to fibrosis. Although transaminase levels are commonly used to assess hepatic inflammation, they may not relate directly to the histology. We developed a noninvasive diagnostic score as an alternative to liver biopsy to help optimize treatment for AIH and monitor disease progress. METHODS: Eighty-two participants with type 1 AIH who had undergone liver biopsy were included (44 in training and 38 in validation sets). Liver histology was assessed according to the histologic activity index (HAI; score 0-18) and Ishak's histologic fibrosis index (HFI; score 0-6). High inflammation was defined as HAI>4, and advanced fibrosis was defined as HFI>2. Routine laboratory test findings and stepwise linear regression were used to develop the best models predicting HAI and HFI. The best cut-off value to predict high inflammation and advanced fibrosis for these formulas was then calculated based on receiver-operating characteristic analysis. RESULTS: The cut-off value for a model predicting high inflammation was ≥3.57 (AUROC = 0.93; 95% CI: 0.86-1.00), with 100% sensitivity and 85% specificity. High inflammation was confirmed with an 81% positive predictive value and excluded with a 100% negative predictive value. In the validation set, the sensitivity, specificity, positive predictive value and negative predictive values were 100, 56, 88 and 100% respectively. The diagnostic yield of the fibrosis score was unsatisfactory. CONCLUSIONS: The noninvasive inflammatory score based on four routine laboratory parameters discriminated patients with and without significant hepatic inflammation and may facilitate follow-up of type 1 AIH patients.

Association of coeliac disease with primary biliary cirrhosis in Poland.

OBJECTIVES: In western and northern but not southern Europe, the prevalence of coeliac disease among patients with primary biliary cirrhosis (PBC) is higher than in the general population. We analysed the prevalence of coeliac disease among patients with PBC in Poland, a central European country. METHODS: In 115 patients with PBC, immunoglobulin A (IgA) antibodies against guinea-pig tissue transglutaminase (tTGA), monkey endomysium (EMA) and gliadin (AGA) were determined. In patients positive for tTGA and/or EMA, the DNA typing of HLA-DQB gene and small-bowel biopsy were performed. RESULTS: IgA EMA was found in one patient with PBC (0.9%, 95% CI 0-2.5%). tTGA was detected in seven patients (6%, 95% CI 1.8-10.3%). Small-bowel biopsy showed flat mucosa in one subject, who was EMA positive/tTGA negative/AGA negative, and normal histology in four tTGA-positive/EMA-negative patients. In the latter four patients, the positive tTGA result was caused by IgA reactivity to proteins other than transglutaminase. Prevalence of coeliac disease in our 115 patients with PBC was 0.9% (95% CI 0-1.9%). In one patient with silent coeliac disease presenting with the HLA-DQ2 allele, introduction of a gluten-free diet was followed by improvement in liver function tests, improvement in histology of the distal duodenum, and disappearance of EMA. CONCLUSIONS: Our results from Poland do not confirm a high prevalence of coeliac disease in PBC patients. Guinea-pig liver transglutaminase immunolinked assay cannot be used as a screening test for coeliac disease in PBC patients. A gluten-free diet may be helpful in restoration of liver function in patients with such an association.