Surrogate markers of bile duct disease progression in primary sclerosing cholangitis - A prospective study with repeated ERCP examinations.

Background & Aims: Validated prognostic tools for estimating short-term bile duct disease progression in primary sclerosing cholangitis (PSC) are lacking. We evaluated the predictive value of serum and biliary biochemistry for the progression of bile duct disease in PSC using repeated endoscopic retrograde cholangiopancreatography (ERCP) examinations to identify surrogate markers for more personalized surveillance. Methods: We conducted a prospective analysis including patients with PSC who underwent ERCP for confirmation of diagnosis, monitoring of disease progression, or dysplasia surveillance. ERCP findings were scored, and dilatation was performed if a dominant stricture was diagnosed or if a cytology brush could not be passed. Bile samples were aspirated for biliary IL8 and calprotectin. We analysed optimal cut-off values and AUCs for 20 laboratory markers and evaluated their association with the time to an ERCP score increase of ≥2 points or first dilatation, whichever came first. Of the 1,002 patients, 653 had ≥2 ERCP examinations and ≥3 years of follow-up. After excluding patients with PSC-overlap syndrome or initial dilatation, 398 patients were included. Results: Of the patients included, 62% had mild or moderate and 38% had advanced bile duct disease. During follow-up, 41% of patients demonstrated progression of disease. Biliary calprotectin (AUC 0.76; 95% CI 0.69 to 0.82) and IL8 (AUC 0.76; 95% CI 0.69 to 0.84) were the only variables that demonstrated predictive value for disease progression and/or need for dilatation. Conclusions: Biliary calprotectin and IL8 are promising surrogate markers for identifying patients with PSC at risk of progression and determining the timing for subsequent imaging. Conventional liver function tests may not be sensitive or specific enough to monitor PSC progression, particularly in the short term. Impact and implications: Validated prognostic tools for estimating short-term bile duct disease progression in primary sclerosing cholangitis are lacking. In this prospective study, based on sequential endoscopic retrograde cholangiopancreatography examinations, biliary calprotectin and IL8 levels turned out to be more sensitive for predicting bile duct progression than traditional liver function tests, such as alkaline phosphatase, in the short term. These findings could lead to more personalized patient surveillance and improve clinical practice by providing a more accurate method for monitoring disease progression and treatment responses. Additionally, these markers have potential as surrogate endpoints in clinical drug trials. The limitation is that measurement of biliary IL8 and calprotectin requires endoscopic retrograde cholangiopancreatography with bile sampling.