The GI-MAP™ | Diagnostic Solutions Laboratory
The GI Microbial Assay Plus (GI-MAP™) assesses a patient's microbiome from a single stool sample, with particular attention to microbes that are well-researched to cause disease or disrupt normal microbial balance and contribute to perturbations in the GI flora and contribute to illness.
What Advantage Does The GI-MAP Offer?
In the last few decades, DNA analysis has transformed the field of microbiology. Culture techniques - previously the standard - leave up to 50% of bacterial species virtually invisible! When next-generation methods revolutionised this field, it allowed the identification of tremendous numbers of previously unknown organisms. For instance, anaerobic bacteria make up a large part of the human microbiome and can be opportunistic and cause illness, therefore, inability to cultivate these organisms left a large blind spot for clinicians when trying to diagnose the source of infection.
Diagnostic Solutions Laboratory, headed by Dr David Brady, is using a novel DNA technique to detect a comprehensive list of stool bacteria, viruses, fungi, and parasites. The method and instrument used is FDA-cleared for the detection of 15 of the most common causes of gastroenteritis and has been clinically validated for use with human stool samples to a superior sensitivity and specificity. This is an automated, multiplex DNA analysis method, allowing for the simultaneous measurement of multiple bacteria, fungi, parasites, and viruses, all from a single sample.
Multiplex Polymerase Chain Reaction (PCR) vs. Culture Techniques
Multiplex PCR makes it possible to simultaneously detect many different organisms in one sample. The automated nature of this method minimises the chance for human error; indeed, this is the only FDA-cleared DNA test for gastrointestinal microbes and pathogens available.
Other stool tests on the market primarily rely on bacterial culture of the stool specimen. A limitation of this method is that only the organisms that grow can be identified, meaning anaerobic organisms and parasites that do not grow under routine culture conditions cannot be identified. This is particularly prevalent with anaerobes like Lactobacillus. Often results of 'NG' or '0+' are reported, but it obviously does not mean it is not present, just simply that it would not grow in the lab, which is also seen with many yeasts and fungi.
A further limitation comes with sensitivity and specificity. The GI-MAP reports many of the organisms as <dl (less than detectable limit). This means that there are less than 100 cells per gram for the organism. It does not mean that the stool sample was necessarily void of that organism, but most bacteria need to be present in higher numbers to cause dysbiosis or disease. In contrast, when culturing bacteria, if there is close to 100 cells per gram it could be reported as positive. This is because when streaking the agar plates, the sample is spread into 4 areas of the plate with slightly less sample in each. If there is growth into the 4th area, even of just a few cells, it is called 4+. Some samples may have 70 cells per gram, grow in the 4th quadrant and get reported as 4+ and others may have 10,000 cells per gram and they would also be 4+.
Hence, collection of stool specimens for DNA analysis most closely represents the actual microbial populations of the patient’s gastrointestinal tract at the time of collection versus culture based methods. This is why it is the methodology of choice for microbiome researchers and now - via Diagnostic Laboratory - to Functional and Integrative Medicine practitioners for better client outcomes.