If you have watery diarrhoea now — especially during or after antibiotics — contact a clinician today. Suspected C. difficile infection is assessed and treated clinically, on a timescale of hours to days. Severe abdominal pain, high fever, blood in stool, or signs of dehydration warrant urgent care. Nothing on this page is a substitute for that, and a stool panel that returns in 10–14 business days is not the right instrument for an acute illness.
Why results seem to disagree
- GDH detects an enzyme nearly all strains make → is the organism here?
- Toxin immunoassay detects toxin protein → is toxin present in this sample?
- PCR/NAAT detects toxin genes → is a toxin-capable strain here?
- Three different questions. Different answers are not necessarily a laboratory error.
Result explainer
What does my combination of results mean?
Set each test to what your report says. This explains what the combination measures — it does not diagnose you and it does not recommend treatment.
Set the tests above to what your report says. Without JavaScript: the table further down this page explains what each test measures, which is what the explainer draws on.
Not medical advice, and not a diagnosis. If you have diarrhoea now — particularly during or after antibiotics — contact a clinician today rather than working from this page.
Clostridioides difficile — still widely written Clostridium difficile, and reclassified into the genus Clostridioides, which is why both names circulate — is a Gram-positive, spore-forming, anaerobic bacterium. It causes disease through toxins, principally toxin A and toxin B. Strains that do not produce toxin do not cause the illness. That single fact is the key to every confusing result below: the organism being present and the organism causing disease are two different findings.
What each test actually measures
| Test | What it detects | The question it answers |
|---|---|---|
| GDH antigen glutamate dehydrogenase | An enzyme produced by essentially all C. difficile strains, toxin-producing or not | Is C. difficile present at all? |
| Toxin A/B immunoassay | The toxin proteins themselves | Is toxin detectable in this sample? |
| PCR / NAAT | The toxin genes — the genetic instructions for making toxin | Is a strain capable of producing toxin present? |
| Toxigenic culture | Grows the organism, then tests whether the isolate produces toxin | Is there a toxin-producing strain, confirmed directly? |
Because these are four different measurements, laboratories generally combine them in a defined sequence rather than relying on one. Which sequence a laboratory uses, and how a given combination should be acted on, follows current clinical guidance and is a matter for the clinicians involved.
GDH positive, toxin negative
This is the single most-searched C. diff result and it is genuinely confusing, so here it is plainly. GDH positive means C. difficile is present. Toxin negative means toxin protein was not detected in that sample. Both can be true at once, and the usual explanations are that the organism is being carried without causing disease, or that toxin is present below what the assay detects.
What that combination means for you depends on something no test reports: whether you are actually ill. The same result pattern in someone with three days of watery diarrhoea and in someone with no symptoms at all does not lead to the same decision. This is precisely why the treat-or-not judgement sits with a clinician who can assess you, and why we are not going to tell you what it means on a web page.
The same reasoning applies to PCR positive, toxin negative: a toxin-capable strain is present, toxin protein was not detected, and your symptoms are the deciding context.
Carriage is common, and it is not the same as infection
C. difficile can be carried in the gut without causing illness. This is why testing people who do not have diarrhoea tends to generate confusion rather than useful information — a positive result in someone with no symptoms is more likely to describe carriage than disease, and treating it is not automatically the right move. Infants in particular are frequently colonised, which is why C. diff testing in babies is approached quite differently.
Two questions people ask after treatment
"Should I be retested to prove it is gone?" Ask the clinician who treated you. Testing again after symptoms have resolved often produces more confusion than clarity, because a test can stay positive while you are perfectly well — meaning a positive retest may tell you nothing actionable while causing considerable worry.
"My test was negative but I still have diarrhoea." Then C. difficile is an unlikely explanation and the search for the actual cause continues with your clinician. A negative C. diff test rules something out; it does not rule anything in. Do not self-treat for C. diff on the strength of it.
Where the GI-MAP fits — and where it does not
The GI-MAP reports C. difficile toxin A and toxin B genes, quantitatively, as part of an 85+ marker panel. Being gene detection, it answers the third question in the table above: whether a toxin-capable strain is present. It does not establish active infection.
And the turnaround settles the rest of the argument. Results come back in approximately 10–14 business days from sample receipt. A suspected acute C. difficile infection cannot wait two weeks. The GI-MAP is not the test for that situation and we will not sell it to you as though it were.
Where a broad panel is genuinely useful is afterwards: antibiotics and a C. difficile episode both disturb the gut, symptoms can persist after the infection is treated, and a practitioner may want a wider quantified view while working through that. See C. difficile: symptoms, testing and recovery and how results are reported.
Recovering from an infection and want a broader picture of your gut? That is what this panel is for.
See pricing → C. diff overview