Introduction IgG4 associated cholangitis (IAC) may have similar radiographic appearances to primary sclerosing cholangitis (PSC) and cholangiocarcinoma (CCA). Making the diagnosis is important as IAC usually responds favourably to steroids (in contrast to PSC) and erroneous treatment for presumed CCA may be avoided. We assessed whether specialists familiar with these diseases could reliably distinguish between them based on endoscopic retrograde cholangiograms (ERC).

Methods ERCs (n=104) of patients with a definitive diagnosis of IAC, PSC and CCA from centres in the US, Japan and UK were screened for quality by an experienced endoscopist unaware of clinical diagnoses. A final set of 48 ERCs (20 IAC, 10 PSC, 10 CCA and 8 duplicates) were arranged in random order and presented to 18 reviewers unaware of the diagnosis. Reviewers noted presence or absence of key ERC features and provided their three most probable diagnoses given as per cent confidence (95%, 75%, 50%, 25% and 5%, totalling 100%). We used a ≥75% confidence in the diagnosis of IAC to determine sensitivity and specificity for that condition. The κ statistic for intra- and inter-observer agreement was also calculated.

Results The specificity of ERC for detecting IAC was high and did not differ significantly between centres (Abstract 061), but sensitivity was uniformly low. Neither reviewer speciality (endoscopist, radiologist, HPB physician) nor years of experience had any statistically significant effect on reporting success. Although intraobserver agreement was generally very good, interobserver agreement was poor (Abstract 061).

Conclusion High specificity for diagnosing IAC using ERC suggests that particular cholangiographic features support the diagnosis. However, poor sensitivity suggests that, based on ERC, many patients with IAC, who might benefit from steroid therapy, may be misdiagnosed with PSC or CCA. Additional diagnostic strategies, including pathological sampling, are likely to be vital in distinguishing these diseases.