How to Test for the Root Cause of Your IBS

Last week we talked about the 5 most common root causes of IBS and how you can have one, or more commonly, multiple triggers from the list. And while the exact root cause, or combination of causes, is unique to each person with ‘IBS’, this week I wanted to share with you the gold-standard testing options for the top five root causes as it stands in 2016. I truly hope that this post gives you all the information you need to request accurate testing for a condition that is very treatable and should NOT be ruining your life. Let’s get into it!

Here is a summary of what we are going to cover:
>  Why you need to test, not guess
>  Gold-standard testing options for the top 5 root causes of IBS
>  How to figure out which tests you need and why your practitioner might request multiple tests (hint, it has to do with increasing the likelihood of you beating IBS permanently)


Why do I need to test?


By now, you’re crystal clear that many of the root cause conditions of IBS have a lot of overlapping symptoms. Which is part of the reason why all of these different conditions have been thought of as one single thing, IBS, for so long. And while we haven’t touched on treatment yet, the critical point here is that all these conditions need to be treated in a different way, particularly when it comes to the right diet and the right supplements. Again, this is one of the reasons why clinical trials looking for a one-size-fits-all treatment for IBS always fail. IBS is not one condition, and there is not one treatment. So how do we figure out the underlying root cause of our own IBS symptoms? Test, don’t guess! Functional lab tests, that is. And while there are countless other tests you can do in more complex cases, here are my four go-to tests that cover-off the 5 most common root causes of IBS we covered last week.


Test #1 – Comprehensive Digestive Stool Analysis (CDSA) + PCR Stool Test


What are we testing for?

There are a whole range of markers on a stool test that help us get a really clear idea about what is going on inside your large intestine that may be contributing to your IBS symptoms. But a stool test also gives us clues about other parts of the digestive system, like the stomach, small intestine and pancreas. This is why I like my clients to start with a simple one-day sample stool test, that they can do at home. But most importantly, a stool test gives us information about whether you have a dysbiosis – imbalance of good, bad and commensal bacteria in the large intestine, and/or a gut infection such as those caused by parasites, bacteria and yeast/fungus.


What are the key markers and what do they mean?

There are two parts to stool testing that are important for detecting the root causes of IBS. First up is the PCR analysis. Science has made great headways and now we have really accurate PCR (Ploymerase Chain Reaction), or DNA/RNA testing, which looks for the proteins of pathogenic (bad) parasites and bacteria in the stool. This approach is gold standard and way more accurate than the traditional approach of using a microscope. From the PCR component of the test we can see whether you have a gut infection, as shown in the image below: ‘Blastocystis species detected’.

The next part of the stool test that is important for detecting the root cause of your IBS is the Beneficial Bacteria Count, Other Bacteria and Yeasts from the CDSA, or microscopic analysis. These sections of the CDSA test tells us whether or not you have a dysbiosis, as well as any other gut infections from parasites, bacteria and yeast/fungus.

You can see in the image below that beneficial bacteria ‘Lactobacilli’, an essential species for the microbiome of the large intestine, is low. We can also see that Other Bacteria have been detected, ‘Klebsiella’ and other un-named species. This means we have not enough of the good guys and too many of the bad guys – a dysbiosis. Added on top of this, we can see ‘Candida albicans’ and ‘Other Yeasts’ detected. These yeasts are considered a gut infection because they have overgrown in the large intestine, most likely as a result of the parasite and dysbiosis. Overall, the parasite, lack of good bacteria, overgrowth of pathogenic bacteria and yeast all contribute in a negative way and are highly correlated with IBS symptoms.


PCR Test Result – Example Extract

CDSA PCR Stool Lab Test Result

CDSA Test Result – Example ExtractCDSA Stool Test Result

Here is a video on the stool testing process in case you are interested:


Test #2 – Lactulose and/or Glucose Breath Test


What are we testing for?

We use a breath test to identify SIBO. I’ve written a separate post on SIBO testing, so there is a lot more information about breath testing there, but here’s the abbreviated version. SIBO is an overgrowth of bacteria, good or bad, in the small intestine. SIBO is highly correlated with bloating (as quickly as 20 minutes after a meal), constipation, diarrhoea, gas and abdominal cramps/pain or gurgling. The current gold standard test we use to detect SIBO is the three-hour lactulose and/or glucose breath test. For both, you take a baseline breath sample, drink a lactulose or glucose solution, then take further breath samples every 20 minutes for three hours. Very easy and can be done at home. If overgrown bacteria are present, they will ferment the lactulose or glucose and produce hydrogen or methane gas, which we can detect and measure in your breath to work out whether you have SIBO, and how large the overgrowth is.


What are the key markers and what do they mean?

With breath testing, interpretation of results isn’t always black and white. With that in mind, here are the key measurements (but not all) we are looking for that may indicate an overgrowth in the small intestine:

Lactulose Breath Test:
> A rise of 20ppm in hydrogen within 120 minutes – Hydrogen Dominant SIBO
> A rise of 12ppm in methane within 120 minutes – Methane Dominant SIBO
> A combined rise in hydrogen and methane of 15ppm within 120 minutes – Mixed SIBO
> Methane measurements of >3ppm at any point during the test if constipation is the dominant symptom – Methane Dominant SIBO

Glucose Breath Test:
> A rise of 12ppm in hydrogen or methane within 120 minutes – Hydrogen/Methane/Mixed SIBO


Lactulose Breath Test Result – Example Extract

SIBO Breath Lab Test Result

Test #3 – Intestinal Permeability Urine Test


What are we testing for?

This next test also focusses on what is happening in the small intestine. Particularly with the intestinal wall, where most of our nutrition is absorbed and all of the ‘bad’ undigested food, pathogens and toxins (macromolecules) are kept away from our blood-stream. We are interested in the integrity of the intestinal wall, and are trying to identify whether it is hyperpermeable (leaky) or not. This is commonly known as a ‘leaky gut’ test, and you can find out more about Leaky Gut in a separate post here. We use a simple urine test where you drink a lactulose and mannitol solution, then collect all urine for the next six hours at home.


What are the key markers and what do they mean?

We use a urine test to measure the ability of these two sugar molecules, Lactulose and Mannitol, to permeate the intestinal lining. But first, it is important to understand the two ways in which your gut can be ‘leaky’:

  1. Particles moving through your damaged epithelial cells (transcellular)
  2. Particles moving between the loosened tight junctions that hold your epithelial cells together (paracellular)


There are three things we are looking for that will explain the ‘phase’ or ‘type’ of leaky gut you have:

  1. Mannitol Recovery: Mannitol is a mini sugar molecule and can move through the epithelial cells easily (transcellular uptake), making it a great marker for the health of cells. Increased or decreased transcellular uptake indicates damaged villi and microvilli, malnutrition from not absorbing nutrients and other associated conditions.
  2. Lactulose Recovery: Lactulose is a large sugar molecule and is a good marker to see whether the tight junctions between the cells are tight or leaky. Increased levels of lactulose are bad and indicate permeability through the intestinal lining between the cells due to loosened tight junctions, leading to maldigestion, malabsorption and malnutrition.
  3. Lactulose:Mannitol Ratio: The lactulose:mannitol ratio is a secondary marker for leaky gut and is only used as an indicator when there is nothing to note from the above two measures.  This ratio comes into play in the early stages of leaky gut, when one number is elevated compared to another which means things are starting to head in the direction of being leaky in the future.


Intestinal Permeability Test Result – Example Extract

Leaky Gut Intestinal Permeability Test Example

Here is a video on the testing process in case you are interested:


Test #4 – IgG Food Sensitivity Dry Blood Spot Tests


What are we testing for?

Sadly, food sensitivities are estimated to affect up to 40% of the population and commonly cause IBS symptoms. Because food sensitivities are dose-dependent and often have delayed symptom onset, identifying them through an elimination diet can be challenging. So I like to use an IgG mediated immune response test as an initial screener. You complete this test by taking a finger-prick blood sample collected at home to help identify the foods that may be causing or contributing to your symptoms. I do want to make a quick note about food sensitivity testing and say that there is currently no perfect test, however an IgG mediated immune response is a good place to start for identifying food triggers, reducing inflammation and eliminating IBS-symptoms.


What are the key markers and what do they mean?

The IgG panel covers 96 foods and measures the level of IgG mediated immune response produced when exposed to the proteins in the food being tested. Basically, any reaction higher than a level three should be avoided for a minimum of three months to reduce inflammation and give the gut lining space to heal.


IgG Food Sensitivity Test Result – Example Extract

IgG Food Sensitivity Test Example

Here is a video on the IgG testing process (the most common food sensitivity test I use) in case you are interested:


So what test do I need?


So, how does your practitioner choose which test is right for you? The simple answer is: that’s what they studied for. The longer answer is that:

  1. The symptoms you have and don’t have are the best (but not perfect) clues about which test you need; and
  2. Some tests can be considered first-line or screening tests, like the CDSA, that help determine what further testing might be required.


For both of these reasons, you might need more than one test, either initially, or as you learn more about the imbalances you have. Some clients like to take a comprehensive approach and do all the appropriate tests at once, while others prefer to take a slower, more progressive approach. As with most things, there are pros and cons to both approaches, it’s why no two healing journeys are the same. But the important thing to remember is- test, don’t guess. Because if you’re guessing, just based on symptoms, you’re likely going to waste a lot of time and money trying to fix things that don’t need to be fixed before you finally hit on the key underlying conditions or imbalances causing your symptoms.

The other benefit of testing is that it gives you a baseline measure to compare subsequent re-tests. That way, when you remove a gut infection, for example, and start to feel better, you can confirm it’s no longer in your system with follow-up testing and be confident in knowing it’s all gone.

So now we know all there is to get us started with testing, we can request the right tests, get our results and move onto treatment. Which we will be covering in great detail next week. I find testing super motivating because it gives you something really clear to work on. I hope you can easily use the content of this blog as a part of your IBS healing journey. And I know you know this, but I’m going to say it anyway; your health is worth it.

If you want to learn more about testing, or how I can help, book in a free 15-minute pre-consultation call and we can have a chat about your health.



Bella Lindemann

Bella is a Certified Functional Diagnostic Nutrition® Practitioner who specialises in working with women with gut infections and associated chronic digestive complaints, fatigue and food sensitivities.

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