April 22, 2024
Fecal Calprotectin Test

Fecal Calprotectin Test: A Comprehensive Guide to Understanding and Interpretation

What is Calprotectin?

Calprotectin is an abundant calcium-binding protein found within the cytosol of neutrophils. It makes up about 60% of the protein content in neutrophils. When neutrophils pass into the intestinal tract as a result of mucosal injury or inflammation, calprotectin is released into surrounding tissues and into the fecal stream. Its levels in stool are directly proportional to the number of neutrophils present in the intestinal tract. Hence, fecal calprotectin levels serve as an excellent marker of intestinal inflammation.

Why measure Fecal Calprotectin?

Fecal calprotectin testing is commonly used for assessment of intestinal inflammation. Some key reasons for measuring fecal calprotectin include:

– Differentiate between irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD): IBS does not involve intestinal inflammation, so fecal calprotectin levels are typically normal in IBS. Elevated levels point towards probable IBD like ulcerative colitis or Crohn’s disease.

– Monitor response to treatment in established IBD: Serial monitoring helps assess response to medications and disease activity over time. Declining calprotectin levels indicate treatment efficacy and decreasing inflammation.

– Detect postoperative recurrence in IBD: Abdominal surgery is often curative, but recurring symptoms require evaluation. Fecal calprotectin can detect subclinical inflammation prior to obvious clinical or endoscopic recurrence.

– Distinguish between infectious and non-infectious causes of diarrhea: Many infectious pathogens cause intestinal inflammation. Elevated calprotectin confirms an inflammatory component beyond basic infectious diarrhea.

– Evaluate disease extent and severity: Higher calprotectin values correlate with more extensive and active inflammatory activity, helping categorize IBD phenotypes.

Fecal Calprotectin Test Process

The basic steps involved in fecal calprotectin testing include:

– Stool sample collection: Fecal Calprotectin Test Patient collects a small stool sample, ideally first morning stool using a collection container.

– Sample transportation: Container is sealed tightly and transported to laboratory within 24 hours for maximum stability. Refrigeration preferred.

– Sample preparation: Laboratory processes and extracts calprotectin from the stool sample. This releases it from complexes to enable measurement.

– Analysis: An enzyme-linked immunosorbent assay (ELISA) is commonly used. It quantifies calprotectin concentration in nanograms of calprotectin per one gram of stool (ng/g).

– Result reporting: Most labs report quantitative results, with a reference range typically <50 ng/g considered normal. Levels >50 ng/g indicate intestinal inflammation.

Fecal Calprotectin Test Interpretation

Proper interpretation of fecal calprotectin results requires correlating the quantitative value with the clinical context and presentation:

– <50ng/g: Lower normal range suggests no or minimal intestinal inflammation. Favors diagnoses like IBS.

– 50-249 ng/g: Mildly elevated, could indicate low-grade inflammation as seen in mild/quiescent IBD. Repeat testing advised.

– 250-499 ng/g: Moderately elevated, suggestive of mild-to-moderate intestinal inflammation. Consistent with active ulcerative colitis or Crohn’s disease.

– 500-1499 ng/g: Significantly elevated, indicative of moderate-to-severe intestinal inflammation. Typically seen with active colitis.

– >1500 ng/g: Very high levels almost always correspond to active intestinal inflammation like severely active ulcerative colitis.

Serial monitoring is valuable to gauge treatment response over time. A declining trend confirms resolution of inflammation with therapies. Clinical correlation is important with all laboratory testing.

1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it