Lettesjö found an elevation of fecal myeloperoxidase in collagenous colitis (median 11.7 μg/g; Q1–Q3: 2.0–124 μg/g) compared to IBS patients (median 1.7 μg/g; Q1–Q3: 0.81–5.2 μg/g), p < 0.01, and healthy controls (median 2.5 μg/g; Q1–Q3:1.1–6.3 μg/g; p < 0.05 [91]. Here, MPO is linked to irritable bowel syndrome.