The Nutritional Supplement

This article is a review of the webinar ‘Exploring the GI-MAP (Gastro-Intestinal Microbial Assay Plus) & Functional GI Diagnostics”, presented by Tony Hoffman, CEO and President and Dr David Brady, Chief Medical Officer of Diagnostic Solutions.  The webinar was organised by Invivo Clinical, the UK distributor for the GI-MAP test and took place on 17^th November 2015.  The webinar is not available to be viewed by those who didn’t attend, although you can register for future webinars and updates at: http://www.invivoclinical.co.uk. 

 

This webinar presented a summary of the GI-MAP test, the rationale behind the biomarkers chosen and the technology behind the test.  Attendees were also provided with a set of handouts, including a 26-page white paper which provides an explanation and rationale for the specific DNA analysis method used by the test and for each of the biomarkers, including sensitivity & specificity data (where appropriate) and supporting research amounting to over 120 references in total. The white paper is also available from the Diagnostic Solutions website.

 

The GI-MAP measures 15 of the most common bacterial, viral and parasitic pathogens known to cause gastroenteritis, plus a comprehensive list of additional bacteria, parasites, fungi and yeast species.  In addition, the test also measures Secretory IgA, anti-gliadin, Pancreatic Elastase 1, lactoferrin and occult blood.

 

Which Technology is Best for Stool Testing?

 

The first part of the webinar focused on the technology behind the test. Many practitioners are still unsure as to which method is best when it comes to stool testing, as there have been reports in the literature that DNA analysis (sometimes referred to as ‘PCR’ which stands for Polymerase Chain Reaction) can be over sensitive, resulting in false positives or detecting microbes in the stool sample and flagging them as ‘positive’ when in fact they were not present at sufficiently high levels to be clinically relevant and may not actually require intervention. Cross-reactivity can also be a problem with DNA analysis leading to issues with specificity.

 

The presenters explained that the method and instruments they use are third-party validated by the FDA (US Food & Drug Administration) and is the same platform used by the major high-end academic centres of excellence, pathology labs and hospital labs across the USA. 

 

Both presenters acknowledged that there have been issues with sensitivity and specificity in the past with DNA analysis.  DNA analysis involves a process called hybridization which is when a single-stranded DNA segment binds to a complementary piece of DNA called a probe. This step is important for accurate identification of a microbe based on its DNA signature.  In the method used by the GI-MAP test, the DNA is hybridized to probes which are attached to magnetic beads, each of which also has its own unique signature. This additional step virtually eliminates all non-specific binding, significantly reducing false positive rates that have been associated with previous DNA methods.

 

The method is completely automated, meaning there is less room for human error, while the turnaround time can be as little as 3-4 days. Furthermore, only one stool sample is required, which can be a significant factor in aiding client compliance, particularly those who may not pass stools regularly.

 

With regard to setting reference ranges for the additional organisms on the panel, samples were collected from almost 100 healthy persons. Then the lab collected patient samples from around seven different clinicians so they could map them against the healthy population.  This gave them a meaningful set of reference ranges. However, with opportunistic organisms (i.e. those which may be pathogenic if present in high enough quantities) there is still a level of interpretation required by the practitioner, combined with patient presentation and case history, to determine whether dysbiosis is present and/or requires intervention.

 

Test Biomarkers

The GI-MAP tests for the 15 most common pathogenic organisms known to cause gastroenteritis:

 

Opportunistic Bacteria

In terms of opportunistic bacteria, the GI-MAP only tests those for which there is significant literature of at least an association of overgrowth, or of elevated recovery of DNA of these organisms, with a specific autoimmune disease. In most cases, evidence of a pathogenic link is supported by the literature.

 

H. Pylori and Virulence Factors

The GI-MAP tests for H. pylori in the stool, but also tests for two virulence factors associated with it: cagA and vacA.  Evidence suggests that H. pylori is not always pathogenic and in some cases may even provide benefits to the host eg. research provided in the White Paper suggests H. pylori may protect the host against certain atopic disorders.  The presence of one or both of the virulence factors (combined with patient presentation and symptoms) are indicative of increased virulence of the H. pylori and that it is therefore much more likely to cause disease and require intervention for its eradication.  References in the white paper also support the increased sensitivity of DNA-based assays for the virulence factors than an antigen test.

 

Potential Autoimmune Triggers

Also included in the GI-MAP are biomarkers which have known associations with autoimmune diseases such as Rheumatoid Arthritis, Ankylosing Spondylitis etc.  While there are likely to be multiple causal factors involved in these conditions, these biomarkers are the antigenic proteins that may stimulate the expression of these conditions in susceptible individuals, so could be useful in determining a patient’s risk of such conditions particularly when viewed alongside family history.

 

One of the biomarkers included in this section is Yersinia enterocolitica because of its known association with autoimmune thyroid diseases such as Hashimoto’s and Grave’s disease.  Yersinia enterocolitica expresses on its surface, proteins that look like TSH receptors on the thyroid so this can cause a cross reaction and lead to autoimmune thyroid destruction over time.

 

Additional Dysbiotic Overgrowth / Bacteria

The presenters explained that there is a 10-20 fold increase in prevalence of Hashimoto’s and other autoimmune diseases in patients with coeliac disease. What they see clinically is that these patients can develop antigen-antibody complexes which have an affinity for the thyroid tissue and then later on they develop affinity for the Central Nervous System, so these patients may not only be at risk of autoimmune thyroiditis but also of early onset dementia, degenerative and neurological conditions like Multiple Sclerosis.  So if a test result showed that a patient had raised levels of Yersinia enterocolitica with raised anti-gliadin and raised SIgA (also included in the GI-MAP), this would be indicative of mucosal intolerance in the GI tract, and could be considered a risk factor not only for autoimmune thyroid disease, but also for other autoimmune diseases and for degenerative and neurological conditions such as dementia and MS.  Again, these results should be combined with family history to see the fuller picture.

 

Additional Markers

The following additional markers are also included in the GI-MAP:

• SIgA
• Anti-Gliadin
• Elastase 1
• Lactoferrin
• Occult Blood

 

Elastase 1 is supported by the research (see White Paper) as a reliable marker for assessing pancreatic output. Dr Brady and Tony Hoffman defended their decision not to include any other pancreatic enzymes in the test as they say the research supports the view that the levels of elastase 1 are indicative of all pancreatic exocrine output.  Another benefit of measuring elastase 1 is that it is not included in most digestive enzyme supplements, so if client is taking any digestive enzymes at the time of the test, they will not interfere with the results.  This is not the case if the test is measuring biomarkers like amylase, trypsin, chymotrypsin, etc. which are typically included in digestive enzyme supplements.

 

Lactoferrin is used to assess presence of inflammation and, according to the presenters, there is as much research to support the accuracy of lactoferrin in this regard as there is research to support calprotectin, so it is a case of using one or the other.

 

Short-Chain Fatty Acids are not included on this test.  The presenters explained that SCFAs have been included in the previous generation of tests because they are influenced by levels of bacterial composition and microbiota, so they were useful secondary markers for assessing levels of beneficial bacteria in the gut.  However, now that it is possible to assess the microbiota directly, it makes no sense to include SCFAs.  Furthermore, SCFAs are also influenced by diet, which reduces their clinical usefulness even further.  The presenters consider pancreatic output and overall microbiota biomarkers to be a more valid indicator of gut health and dysbiosis.

 

Summary

The biomarkers included in the GI-MAP appear to be comprehensive and clinically useful, and supported by evidence.  The presenters gave robust explanations as to the choice behind including, or not including, certain biomarkers.

 

The specific type of DNA analysis method and instrument used for the GI-MAP is FDA-cleared for the detection of the 15 most common bacterial, viral and parasitical causes of gastroenteritis.  With regard to the additional organisms and biomarkers included in the GI-MAP, Diagnostic Solutions are keen to point out that other methods for stool testing (eg. MALDI-TOF) rely on the culture method which is limited by its ability to only measure microbes which can grow in culture. Anaerobic bacteria and yeasts are notoriously difficult to grow in culture which may result in false negatives.  It is worth noting, however, that MALDI-TOF is also an FDA validated platform.

 

It would seem that the DNA technology used for stool testing has certainly moved on from the issues of over-sensitivity and non-specific binding and the fact that the technology used by the GI-MAP is third-party validated by the FDA suggests it is as robust as it can possibly be.  However, it was not clear from this webinar whether the FDA validation applies to all biomarkers on the GI-MAP or only the 15 most common pathogenic bacteria, viruses and parasites involved in the aetiology of gastroenteritis.  With regard to some of the additional organisms, a number of renowned laboratories still use the MALDI-TOF method, also an FDA validated platform, and support their decision with scientific evidence, while others, such as the GI Effects stool test offered by Genova Diagnostics, use a combination of PCR and MALDI-TOF technology depending on the biomarker being measured. Whichever test is used, the important take-home point to remember is that all test results should be interpreted alongside the client's case history and presenting symptoms in order to establish the most appropriate rationale for intervention.