Factors Associated With Loss of Fecal Biomarker Accuracy During Routine Assessment of Inflammatory Bowel Disease

Fecal calprotectin (fCal) and fecal myeloperoxidase (fMPO) have been proposed as biomarkers for monitoring inflammatory bowel disease (IBD); however, their reliability is not fully established. This study investigated clinical variables associated with the loss of accuracy of fecal biomarkers.

Post hoc analyses were performed on previously reported data (New indicators of disease activity in IBD (NIDA-IBD) cohort), which examined fecal biomarkers in individuals with IBD undergoing colonoscopy. Positive and negative results were recorded using previously identified thresholds (fCal, 150 μg/g; fMPO, 8 μg/g). Univariable logistic regression analyses were used to identify clinical variables (patient demographics, disease location and duration, symptoms and medication use) associated with false-positive and false-negative results. Subgroup analyses (Mann-Whitney U test) were performed to establish if the presence of colonic pseudopolyps was associated with fCal and fMPO concentrations in those with endoscopically inactive disease.

One hundred and seventy individuals from the NIDA-IBD cohort were included for analyses (CD, n = 98; female, n = 90; median disease duration 13 years). No clinical variables investigated were associated with a false positive or false negative result. Pseudopolyp presence was not associated with fCal or fMPO concentrations in those with endoscopically inactive disease. Positive and negative predictive values were higher using fecal biomarkers in combination with symptom scores than using symptom scores alone in predicting/excluding endoscopic activity.

No clinical variables were found to be associated with loss of biomarker accuracy, including fecal myeloperoxidase at widely used thresholds. Fecal biomarkers improved prediction of disease activity.