Measurement · Validated against a defined reference standard
Faecal calprotectin: what it measures, and what it does not
Neutrophil-derived calprotectin in stool, tracking neutrophilic intestinal inflammation.
What it measures
Neutrophil-derived calprotectin in stool, tracking neutrophilic intestinal inflammation.
Compartment sampled: Stool, reflecting neutrophil migration into the intestinal lumen.
Assay principle: Immunoassay of the calprotectin heterodimer released by neutrophils, reported per gram of stool.
What it does not measure
It does not localise inflammation, distinguish its cause, or exclude non-neutrophilic mucosal problems. It is not a microbiome measure.
Sources of variance
Each of the following can change the reported number without any change in the underlying biology.
- NSAID use
- Infection
- Age
- Sampling variability between bowel movements
The common misinterpretation
Treating a normal value as evidence that nothing is wrong with the gut, or an elevated value as a specific diagnosis.
What one result cannot establish
- Where in the bowel neutrophilic inflammation is occurring.
- The cause of an elevation, which can include infection and NSAID exposure as well as inflammatory bowel disease.
- That a normal value excludes non-neutrophilic mucosal disease or functional symptoms.
What repeated results would mean
- Serial values are the most interpretable of the stool measures here, because the analyte and its cell of origin are defined.
- A trend still describes neutrophilic inflammation only; it does not describe the microbiome, barrier function, or symptom cause.
- Interpretation of a series belongs to the treating clinician.
How BiomeLogic uses it
Recognised as one of the better-validated stool measures and used to keep discussion anchored to inflammation that is actually measurable. Interpretation belongs to the treating clinician.
Validity class recorded in the BiomeLogic measurement registry: Validated against a defined reference standard (BL-MEAS-0004).
Evidence boundary matrix
The boundary of this measurement, stated as propositions rather than as a verdict on any result.
| Proposition | Population / model | Evidence class | What it supports | What it does NOT support | Sources |
|---|---|---|---|---|---|
| Faecal calprotectin reports the quantity described above. | Stool, reflecting neutrophil migration into the intestinal lumen. | Validated against a defined reference standard | Neutrophil-derived calprotectin in stool, tracking neutrophilic intestinal inflammation. | It does not localise inflammation, distinguish its cause, or exclude non-neutrophilic mucosal problems. It is not a microbiome measure. | — |
| A single faecal calprotectin value describes the person's underlying state. | Stool, reflecting neutrophil migration into the intestinal lumen. | Not supported by the measurement | A description of the sample that was assayed. | Where in the bowel neutrophilic inflammation is occurring. The cause of an elevation, which can include infection and NSAID exposure as well as inflammatory bowel disease. That a normal value excludes non-neutrophilic mucosal disease or functional symptoms. | — |
Question answered on this page
What does faecal calprotectin actually measure?
Short answer
Neutrophil-derived calprotectin in stool, tracking neutrophilic intestinal inflammation. It does not localise inflammation, distinguish its cause, or exclude non-neutrophilic mucosal problems. It is not a microbiome measure. In the BiomeLogic measurement registry it is recorded as: validated against a defined reference standard.
What is established
Neutrophil-derived calprotectin in stool, tracking neutrophilic intestinal inflammation.
Population / model: Stool, reflecting neutrophil migration into the intestinal lumen..
What human evidence shows
No direct human evidence is claimed for this question.
What experimental / non-human evidence shows
No animal or in-vitro evidence is claimed for this question.
Alternative explanations
The measurement is read as a proxy for the biology of interest
Treating a normal value as evidence that nothing is wrong with the gut, or an elevated value as a specific diagnosis.
The measurement is read as a description of the sample assayed
This reading stays inside what the assay detects. It does not localise inflammation, distinguish its cause, or exclude non-neutrophilic mucosal problems. It is not a microbiome measure.
What is not yet known
- Where in the bowel neutrophilic inflammation is occurring.
- The cause of an elevation, which can include infection and NSAID exposure as well as inflammatory bowel disease.
- That a normal value excludes non-neutrophilic mucosal disease or functional symptoms.
What evidence would discriminate these explanations
- Serial values are the most interpretable of the stool measures here, because the analyte and its cell of origin are defined.
- A trend still describes neutrophilic inflammation only; it does not describe the microbiome, barrier function, or symptom cause.
- Interpretation of a series belongs to the treating clinician.
Sources
No references are cited on this page.
What this page does NOT establish
- Any interpretation of an individual reader's result.
- A reference range, cut-off, or decision threshold.
- That this test should or should not be performed.
Educational systems-biology material. Not medical advice, not a diagnosis, and not a treatment recommendation. No dosing, protocol, or personal lab interpretation is given here.
Page provenance
- Canonical title
- Faecal calprotectin: what it measures and what it does not
- Canonical URL
- https://biomelogic.net/measurements/faecal-calprotectin
- Author
- Mohammed Attallah — Systems Biology Consultant
- Publisher
- BiomeLogic
- Version
- 1.0
- First published
- n.d.
- Last substantive revision
- n.d.
- Last evidence review
- n.d.
- Evidence classes present
- Assay validation literature; Clinical consensus / methodology; BiomeLogic editorial classification
- Publication-eligible references
- 0 of 0
Scope
A vendor-independent account of faecal calprotectin: the quantity detected, the compartment sampled, the sources of variance, the inference limits of one result, and the reading the measurement does not support.
What this page does not establish
- Interpretation of a reader's own result.
- Thresholds, ranges, or cut-offs.
- A recommendation to order, repeat, or avoid this test.
Cite this page
Mohammed Attallah (n.d.). Faecal calprotectin: what it measures and what it does not (Version 1.0). BiomeLogic. https://biomelogic.net/measurements/faecal-calprotectin
External citation packet
- Stable URL
- https://biomelogic.net/measurements/faecal-calprotectin
- Scope
- What faecal calprotectin physically detects, and the inferences it cannot support.
- Established vs BiomeLogic inference
- Established: Neutrophil-derived calprotectin in stool, tracking neutrophilic intestinal inflammation. — BiomeLogic inference: that validated against a defined reference standard is the appropriate validity class for this measure — a BiomeLogic editorial classification, not a published grading
- Key references
- None publication-eligible yet.
- Exact citation text
- Mohammed Attallah (n.d.). Faecal calprotectin: what it measures and what it does not (Version 1.0). BiomeLogic. https://biomelogic.net/measurements/faecal-calprotectin