The Neurotoxic Metabolite Test (NMT) was developed by Belgian scientist Professor Kenny de Meirleir and is produced and distributed by Protea biopharma. Currently (October 2009) it has not yet been approved as a clinical diagnostic test and is therefore considered for research purposes only. However, many physicians treating have shown much interest in the test and it is now available through some of these and other distributors such as ProHealth Inc.

The NMT aims to detect the presence of abnormal metabolites in the urine. These metabolites are related to the production of hydrogen sulfide (H₂S). Low levels of H₂S in the body are normal as this gas is used much like nitric oxide (NO) and carbon monoxide (CO) as a signaling molecule. It is involved in the the regulation of blood pressure, neurotransmission, muscle relaxation, and inflammation. It also controls blood flow to the brain ad modulates the hypothalamic-pituitary-adrenal (HPA) axis - the stress control system. However in higher concentrations H₂S becomes a potent toxin. Certain bacteria in the gut produce H₂S which is then absorbed into the body. Therefore the NMT is designed to detect raised H₂S concentrations associated with the growth of these gut bacteria.

Professor de Meirleir found that high urinary H₂S metabolites are associated with overgrowth of Streptococcus, Enterococcus, and Pretovella bacteria in the gut. These bacteria ferment the food we eat to produce H₂S. An overgrowth of such gut bacteria is termed 'gut dysbiosis'. Furthermore, Professor de Meirleir found that a significant proportion of chronic fatigue syndrome (ME/CFS) patients have such dysbiosis and test positive with the NMT test. The test is therefore aimed primarily at ME/CFS patients, although presumably it may also be useful in related conditions such as fibromyalgia.

Abnormally high concentrations of H₂S have many detrimental effects in the body. In animal studies they have been shown to produce a hibernation-like state with decreased core body temperature, sleep apnea, reduced heart and respiratory rates, and a marked metabolic drop; symptoms familiar to those with CFS/ME and fibromyalgia. H₂S also acts as a mitochondrial poison by inhibiting many enzymes involved in the production of ATP (energy). It also interferes with oxygen transport in red blood cells and the use of oxygen by the mitochondria. Also important in ME/CFS is the fact that H₂S inhibits immune cells such as natural killer (NK) cells and T-lymphocytes and disrupts the HPA-axis.

Professor de Meirlier points out that high H₂S may also result from metabolic disorders so these must be ruled out but a positive result in ME/CFS patients is likely to be indicative of gut dysbiosis with the H₂S-producing bacteria named previously. Appropriate treatment may help such patients and is likely to involve antibiotics (natural or pharmaceutical) along with probiotics to restore the beneficial gut microflora.

The test itself is carried out at home and simply involves collecting a sample of first morning urine and adding a small amount to a plastic vile containing a special chemical reactant. If high levels of H₂S metabolites are present the solution will change colour within 3 minutes.

The comprehensive digestive stool analysis (CDSA) is a stool test offered by various labs that may help you and your health care provider uncover underlying causes for chronic symptoms and illness, both digestive and systemic. As with most functional laboratory tests it is most often used when conventional diagnostic testing has failed to provide an explanation for a patient's health concerns, however it can also provide early indication of the development of conditions such as pancreatitis, inflammatory bowel disease (IBD), and colon cancer risk, for example.

The test requires the patient to collect a single stool sample at home and mail it back to the lab in the container and envelope provided. The sample is then analyzed and the results and interpretive report returned to the patient's health care provider.


What the CDSA Measures

The CDSA is indeed "comprehensive" and looks at quite a large number of different markers of gastrointestinal health. These fall into several groups:

Digestion
The pancreas is the organ responsible for secreting the vast majority of digestive enzymes into the GI tract which act on food to break it down into smaller and smaller pieces which can ultimately be absorbed by the body as individual nutrients(the process of digestion). The CDSA measures substances such as chymotrypsin (a digestive enzyme) which give an idea of general pancreatic function and how well the digestive process is working. Additionally putrefactive short-chain fatty acids (SCFAs) are measured. These are produced by certain bacteria in the colon and would be high if digestion was poor in which case the bacteria would have a rich supply of food themselves. Finally the stool sample is examined for evidence of undigested meat and vegetable fibres which obviously would indicate poor digestion.

Absorption
A range of markers are tested for to determine if the body is absorbing nutrients from food correctly. These markers are generally fats/lipids which are easy to detect and provide a good overal picture of absorptive capacity - they include triclycerides, long-chain fatty acids, cholesterol, phospholipids, and total faecal fat. If these are found in high levels in the stool it could indicate poor digestion due to enzyme or bile deficiency, damage (e.g. inflammation) to the absorptive lining of the small intestine, or a fast transit time (e.g. diarrhoea).

Metabolic Markers
These mainly focus on factors influenced by the gut microflora, the bacteria, yeast, and other microorganisms that inhabit the gut. The CDSA measures things such as levels of beneficial SCFAs and the relative amounts of the different types, stool pH, and beta-glucuronidase. Beneficial SCFAs are produced by beneficial bacteria such as Bifidobacteria and Lactobacilli as they metabolise dietary fibre and serve to maintain a stool pH unfavourable to pathogens (slightly acidic), provide fuel to intestinal cells, and reduce inflammation, amongst other functions. Beta-glucuronidase is an enzyme produced by the human body as well as by certain unfavourable gut bacteria. High levels can lead to increased recirculation of toxins, steroid hormones, drugs, and cancer-causing substances in the body.

Microbiology
The lab takes cultures from the stool sample to determine levels of microorganisms present in the GI tract. Gut microflora tested for include both beneficial bacteria such as Bifidobacterium, Lactobacilli, and beneficial strains on E.coli, additional bacteria such as Streptococcus, bacteria which may become pathogenic at high levels including Citrobacter, Enterobacter, and Klebsiella, and bacteria which are considered pathogens at any level including pathogenic E.coli strains, Campylobacter, and Clostridium. As well as bacteria levels of yeasts and fungi such as Candida are also tested for. Most labs in addition to detecting potentially pathogenic microoganisms will provide information on the best prescription and natural substances to eradicate them based on sensitivity testing.

Immunology
Various indicators of gut immunity are tested for including secretory IgA (sIgA), the antibody responsible for protecting the mucous membranes of the body (e.g. the GI tract) from pathogens. Other markers of gut immunity include lactoferrin which binds iron and prevents it being used by undesirable gut microflora, and various substances released bywhite blood cells (WBCs) which indicate inflammation at high levels.

Macroscopic Markers
Finally the stool sample is examined for blood, mucous, and colour to provide further information about GI health.


Uses for the CDSA

The CDSA has many uses but is most often used by integrative or complementary/alternative medicine practitioners for the diagnosis of the underlying causes of chronic health problems including irritable bowel syndrome (IBS) and chronic fatigue syndrome (ME/CFS), particularly problems with digestion and absorption, food allergies/intolerances, and disturbances in the gut microflora such as small intestinal bacterial overgrowth (SIBO), Candida overgrowth, and deficiency of beneficial/probiotic bacteria.

In some instances the CDSA may indicate the need for further testing for serious disease such as Cancer, IBD, or coeliac disease.