LAUSR

BACKGROUND Response evaluation after induction therapy with ustekinumab (UST) in Crohn's disease (CD) is important for decisions on maintenance therapy. We aimed to assess the potential of fecal calprotectin (FC) levels to predict endoscopic response at week 16. METHODS CD patients with FC >100 µg/g and endoscopic active disease (SES-CD> 2, Rutgeerts' score ≥ i2) at initiation of UST therapy were enrolled. FC was determined at weeks 0, 2, 4, 8 and 16 and patients underwent a colonoscopy at week 16. The primary outcome was an endoscopic response at week 16 (SES-CD score ≥50% decrease or a decrease of ≥1 points in Rutgeerts' score). The optimal cut-off levels of FC and change in FC to predict endoscopic response were determined using ROC statistics. RESULTS 59 CD patients were included. Endoscopic response was observed in 21/59 (36%) patients. The diagnostic accuracy for FC levels at week 8 to predict endoscopic response at week 16 showed a predictive value of 0.71. A decrease in FC levels ≥500 µg/g between baseline at week 8 indicates endoscopic response (PPV = 89%), whereas absence of any decrease indicates endoscopic non-response after induction (NPV = 81%). CONCLUSIONS Continuation of UST therapy without endoscopic response evaluation may be considered in patients with a decrease in FC levels of ≥500 µg/g at week 8. The decision on continuation of UST therapy or therapy optimization needs reconsideration in patients without a decrease of FC level. In all other patients, endoscopic response evaluation of induction therapy remains essential for therapeutic decisions.