Each test is graded:Strong trial or consistent human evidence Mixed some human evidence, inconsistent Mechanistic plausible mechanism, mostly animal or lab Weak / against little support, or evidence against
FDN organises dysfunction under H.I.D.D.E.N.: Hormones, Immune, Digestion, Detoxification, Energy and Nervous system. Each test looks at some of these systems and not others, and each rests on a different depth of validation.
| Test | Hormones | Immune | Digestion | Detox | Energy | Nervous system |
|---|---|---|---|---|---|---|
| Hormones (DUTCH) | ||||||
| Stool (GI-MAP) | ||||||
| Organic acids (OAT) | ||||||
| Food panel | ||||||
| Blood chemistry (TDG addition) |
A dot means the test gives direct markers for that system. This is my mapping, not FDN’s, and the grades are mine too: they reflect how I use each test in my own practice.
How far each test can be trusted on its own
Mixed Hormones (DUTCH)
Dried urine hormones and their metabolites, plus the daily cortisol pattern. Urine and blood agree well for some hormones and less well for others, and the ranges are the laboratory’s own.Mixed Stool (GI-MAP)
PCR for named organisms. Detecting a pathogen is meaningful. Commensal “high” and “low” flags use laboratory-set ranges without outcome data. Calprotectin on the panel is well validated.Mixed Organic acids (OAT)
Urine metabolites. Some markers are well established, such as methylmalonic acid for B12 status. Many others rely on the laboratory’s own ranges.Weak / against Food panel
IgG to foods mostly reflects exposure, and allergy bodies advise against using it to diagnose intolerance. At most, it is a prompt for a structured elimination and reintroduction.Strong Blood chemistry
Standard, externally quality-controlled tests with population reference ranges and clinical guidance behind them. This is the layer TDG adds to the FDN set, and the one with the strongest validation.Why five, not one
No single test here is strong enough to act on alone, apart from the blood chemistry. The value is in agreement: when the history, a well-validated blood marker and a functional pattern point the same way, the finding is worth acting on. When they disagree, the stronger test wins.
How the tests are used in the UK
Which labs supply each test here, and what substitutions UK practice needs.
Sources
- Stapel SO et al. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy 2008;63:793–6. PMID 18489614. doi:10.1111/j.1398-9995.2008.01705.x
- NICE DG11. Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel. nice.org.uk/guidance/dg11
- Blood chemistry reference ranges: see the blood chemistry guide for sources per marker.