What does stool calprotectin mean?

From the Guidelines

Stool calprotectin is a reliable marker of inflammation in the intestines, with levels below 50 μg/g considered normal, 50-120 μg/g borderline, and above 120 μg/g suggesting significant inflammation, as supported by the most recent study 1.

Key Points

• Stool calprotectin is a protein released by white blood cells in the intestines during inflammation.
• The test is non-invasive, requiring only a small stool sample, and is useful for distinguishing between inflammatory bowel diseases (IBD) and non-inflammatory conditions.
• Normal calprotectin levels are typically below 50 μg/g of stool.
• Levels between 50-120 μg/g are considered borderline, and values above 120 μg/g suggest significant inflammation.
• The test is valuable for monitoring disease activity and treatment response in patients with known IBD, as shown in studies 1.

Clinical Application

• Stool calprotectin can be used to rule out moderate to severe endoscopically active disease in patients with ulcerative colitis, with a cutoff of <50 mg/g having a sensitivity of 78% and specificity of 57% 1.
• The test can also be used to monitor disease activity and treatment response in patients with IBD, with elevated levels suggesting active inflammation.
• However, the certainty of evidence for the use of stool calprotectin in clinical practice is generally low to very low, due to high unexplained heterogeneity and selective inclusion of studies reporting cutoffs 1.

Limitations

• The test is not perfect, with false positives and false negatives possible, and the certainty of evidence for its use is generally low to very low.
• The optimal cutoff value for stool calprotectin is not well established, with different studies suggesting different cutoffs 1.
• Further research is needed to fully understand the clinical utility of stool calprotectin and to establish clear guidelines for its use in clinical practice.

From the Research

Definition and Purpose of Stool Calprotectin

• Stool calprotectin is a biomarker used to detect intestinal inflammation, particularly in inflammatory bowel disease (IBD) 2, 3, 4, 5, 6.
• It is a protein found in the stool that is elevated in infectious and inflammatory conditions, including IBD 2.
• The measurement of fecal calprotectin is used to distinguish patients with IBD from those with irritable bowel syndrome (IBS) 4, 5.

Clinical Significance of Stool Calprotectin

• Stool calprotectin levels correlate well with histological inflammation as detected by colonoscopy with biopsies 2, 3.
• It has excellent negative predictive value in ruling out IBD in undiagnosed, symptomatic patients 2, 3.
• Fecal calprotectin can be used to monitor the natural course of IBD, predict relapse, and assess response to treatment 3, 6.
• It can also be used to assess mucosal healing, which is a therapeutic goal in IBD management 3.

Diagnostic Accuracy of Stool Calprotectin

• The sensitivity and specificity of fecal calprotectin in differentiating IBD from IBS are 91.1% and 86.7%, respectively 5.
• The test accuracy is 88.9%, and the area under the ROC curve is 0.959 (95% CI, 0.909 to 1.0) 5.
• Fecal calprotectin has been shown to consistently differentiate IBD from IBS because it has excellent negative predictive value in ruling out IBD in undiagnosed, symptomatic patients 2, 3.