BACKGROUND: Fecal biomarkers have emerged as an important tool for assessing and 
monitoring disease activity in patients with inflammatory bowel diseases (IBDs). 
We performed a prospective head-to-head comparison of the diagnostic accuracy of 
both fecal calprotectin (fCal) and neopterin (fNeo), and serum C-reactive 
protein in predicting endoscopic disease severity in patients with IBD.
METHODS: A total of 133 consecutive patients with IBD (78 Crohn's disease [CD] 
and 55 ulcerative colitis [UC]) undergoing a colonoscopy provided fecal samples 
for the measurement of fCal and fNeo concentrations and a blood sample for the 
serum C-reactive protein measurement. Endoscopic disease activities were scored 
independently according to the Simple Endoscopic Score for CD in patients with 
CD and to the Rachmilewitz Index in patients with UC. The respective 
performances of the fecal markers with respect to endoscopic disease severity 
were assessed by computing correlations, sensitivities, specificities, and 
overall accuracies at adjusted cutoffs and also test operating characteristics.
RESULTS: The fCal and fNeo concentrations differed significantly in clinically 
and endoscopically active IBD when compared with those in patients with inactive 
disease. Both fCal and fNeo concentrations correlated closer with endoscopic 
scores in UC (r = 0.75 and r = 0.72, respectively; P < 0.0001 for both) than in 
CD (r = 0.53 and r = 0.47, respectively; P < 0.0001 for both). Using cutoffs of 
250 μg/g for fCal and 200 pmol/g for fNeo, both fecal markers had similar 
overall accuracies to predict endoscopic activity in patients with CD (74%) and 
also a higher and similar accuracies (88% and 90%, respectively) in patients 
with UC, whereas accuracies of C-reactive protein were slightly lower in 
patients with CD and UC.
CONCLUSIONS: The fNeo is a novel reliable surrogate biomarker with the potential 
to identify patients with IBD with active mucosal lesions and represents an 
alternative marker as accurate as fCal to predict and monitor the severity of 
mucosal damages in patients with IBD.