What is the difference between functional and diagnostic testing?
Functional testing assesses system function and optimisation; diagnostic testing identifies disease.
What is meant by “optimal range”?
A narrower range reflecting ideal physiological function rather than population average.
What is the “rule of 3” in functional testing?
Correlate symptoms + lab findings + additional markers before concluding dysfunction.
Why must functional tests be interpreted in context?
They are a snapshot in time and must match symptoms, diet and case history.
What does calprotectin measure?
Gastrointestinal inflammation (leukocyte activity in GI wall).
What calprotectin level requires referral?
> 175 µg/g (repeat test and refer if still elevated).
What does pancreatic elastase measure?
Exocrine pancreatic digestive enzyme output.
What does elastase <200 µg/g indicate?
Digestive insufficiency / exocrine pancreatic insufficiency.
What does severe pancreatic insufficiency look like on elastase?
<100 µg/g.
What does low sIgA indicate?
Reduced mucosal immunity, chronic stress or chronicity.
What does high sIgA indicate?
Upregulated immune response (e.g. acute infection).
What does high zonulin suggest?
Increased intestinal permeability.
What are SCFAs?
Short-chain fatty acids (butyrate, acetate, propionate) produced from fibre fermentation.
Why is butyrate important?
It fuels colonocytes and supports intestinal barrier integrity.
What does low Akkermansia muciniphila suggest?
Impaired mucosal barrier and risk of metabolic endotoxaemia.
Which bacteria produce methane gas?
Methanobrevibacter smithii.
Which bacteria produce hydrogen sulphide gas?
Desulfovibrio spp. and Bilophila wadsworthia.
What defines SIBO?
> 10^5 CFU/ml bacteria in the small intestine.
What rise indicates hydrogen-positive SIBO?
≥20 ppm before 90 minutes.
What rise indicates methane-positive SIBO?
≥12 ppm before 90 minutes.
Why is 90 minutes important in SIBO testing?
It marks transition to the large intestine.
What does OAT measure directly?
Organic acid metabolites (not vitamin levels).
When is OAT useful?
Chronic fatigue, mitochondrial dysfunction, mood disorders, suspected nutrient deficiencies.
What is a limitation of OAT?
Diet at time of testing can significantly alter results.
