Otherindependent cross-checkabstract checked I-WHT-123 standard review
Common blood tests for zonulin do not actually measure zonulin
Serum zonulin as a marker of intestinal mucosal barrier function: May not be what it seems.
Overview
Ajamian M et al.. PLoS One 2019 · PMID 30640940 · DOI 10.1371/journal.pone.0210728
Analysis showed two widely used commercial zonulin tests detect other proteins (haptoglobin, complement C3).
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Validate zonulin tests.
- How was the study done?
Laboratory protein analysis.
- How many people, animals or samples were studied?
Sera samples.
- What was actually found?
Kits detect other proteins.
- How large was the observed effect?
not applicable
- What do the results mean in everyday life?
Be cautious with "leaky gut" zonulin claims.
- What are the study's limitations?
Two kits.
- What does it say about Elawady's specific claim?
Weakens extrapolation of the zonulin pathway.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Does not disprove the biopsy findings.
Scientific in-depth review
1. Full reference
- Authors
- Ajamian M et al.
- Journal
- PLoS One
- Year
- 2019
- Identifier
- PMID 30640940 DOI 10.1371/journal.pone.0210728 · PMC6331146
- Verification
- verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
No competing interests declared.
2. Research question
Do commercial serum zonulin assays detect zonulin?
3. Study design and population
- Study design
- Other – Laboratory assay validation study
- Population
Patients with GI dysfunction and healthy individuals (sera)
- Country
not stated in abstract
- Period
not stated in abstract
- Sample size
not stated in abstract
- Inclusion and exclusion criteria
not stated in abstract
4. Methods and endpoints
- Exposure / intervention
Commercial zonulin ELISA kits (CUSABIO; Immundiagnostik)
- Comparator
Mass spectrometry identification
- Endpoints
Identity of detected antigen
- Statistical methods
Immunoprecipitation, mass spectrometry, SDS-PAGE
5. Actual results
- Results
Commercial assays did not detect zonulin (prehaptoglobin-2): top matches were haptoglobin and complement C3 (CUSABIO) and complement C3 (Immundiagnostik).
- Absolute risks
not reported
- Authors' conclusion
Current commercial zonulin assays do not detect the actual protein; caution is advised when using serum zonulin as a barrier marker.
6. Strengths
- Direct analytical test
7. Weaknesses
- Two kits only
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Analytical study.
9. Assessment of the statistical interpretation
not applicable
10. Relevance to the specific claim
Many human "zonulin" findings rest on assays that do not measure zonulin, weakening extrapolation of the zonulin pathway to population health claims.
11. Independent contrary findings
Biopsy-based studies (A-WHT-16/17) did not rely on serum ELISAs.
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Important methodological caveat.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | low |
| Precision of results | not applicable |
| Directness | indirect |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Validated assays.