Faecal calprotectin is a useful technique for detecting activity in patients with ulcerative colitis. However, there may be high levels due to factors other than the activity of ulcerative colitis. Our aim was to analyse possible false positive results of calprotectin for the activity of ulcerative colitis owing to the presence of inflammatory polyps.
Retrospective, observational, descriptive study. Data was collected from patients monitored for 2 years in whom a colonoscopy had been requested within 3 months after detecting high calprotectin values (>150μg/g) and before modifying the treatment.
We reviewed 39 patients and in 5 of them, with previous diagnosis of extensive ulcerative colitis, inflammatory polyps were detected. Three patients were on treatment with mesalazine, one with azathioprine and other with infliximab. All of them were asymptomatic and the endoscopy did not show macroscopic activity (endoscopic Mayo score=0) or histological activity. The median values of calprotectin were 422μg/g (IQR: 298-2,408) and they remained elevated in a second measurement. In 4 of the patients the inflammatory polyps were multiple and small in size. The other patient had a polyp measuring 4cm.
In clinical practice we can find high faecal calprotectin levels not due to the presence of ulcerative colitis activity, but due to other lesions such as inflammatory polyps. This fact must be taken into account before carrying out relevant changes such as step-up therapy to immunosuppressive drugs or biological drugs in patients with confirmed high calprotectin levels.