How to get an IBS Diagnosis

Getting an IBS diagnosis may seem like a minefield! 

What tests do you need to get? Is it going to be expensive? What about those allergy blood tests that you have seen online?

All the different information can be confusing, and you may feel vulnerable. This post will cover the British medical guidelines for getting and an IBS diagnosis. It will also cover what tests are not recommended.

ESSENTIAL TESTING FOR AN IBS DIAGNOSIS

There is no one specific test to confirm IBS. IBS is a collection of symptoms and does not involve the immune system or inflammation. Therefore, there is nothing to test.

Instead, we rule out other conditions such as coeliac disease, inflammatory bowel disease, or even cancer. Testing to rule out other conditions follows NICE guidelines (1). Click here to read more about what are the symptoms of IBS.

TESTING FOR IBS CHECKLIST

After your doctor has assessed your IBS symptoms, here is a simple checklist for IBS testing for you (1):

1. Erythrocyte sedimentation rate (ESR)
2. C-Reactive protein (CRP)
3. Coeliac disease screening
4. White blood count (WBC)
5. Faecal Calprotectin

When assessing your IBS symptoms, your doctor may take into consideration different symptoms experienced based on your gender. Read more here about about IBS symptoms in females and IBS symptoms in males.

TESTING FOR INFLAMMATION IN IBS DIAGNOSIS

To test for inflammation, blood tests known as c-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) will be needed (2). Both test results would be higher in conditions such as IBD, amongst others.

When you get the test results back for these two inflammatory markers, you will want to know what they mean:

• ESR indicates how quickly the red blood cells will settle in the blood; the higher this rate is, the more likely there is inflammation in the body. 
• The normal range for CRP is <10 mg/L (3). 

Both these tests indicate inflammation in the body but do not pinpoint where the inflammation stems from.

CHECKING FOR INFECTION – IN AN IBS DIAGNOSIS

A raised white blood cell count can be a sign of infection. The role of white blood cells is to protect your body against infection (4). 

The normal range for white blood cells is 3.6-11.0×109/L (5). Please note these reference ranges differ between medical providers.

A COELIAC DISEASE SCREEN

Coeliac disease is an autoimmune condition, this means that the body’s immune system attacks its own system when gluten is consumed. 1 in 100 people have this condition in the UK (6). 

When testing for IBS we must screen for coeliac disease as symptoms of IBS and coeliac disease are similar (7).

The blood tests required to diagnose coeliac disease test for specific antibodies known as total immunological immunoglobulin A (IgA) and IgA tissue transglutaminase (TTG). If these come back as raised, this indicates coeliac disease (8). 

We must test for both of these antibodies as IgA deficiency is more common in those with coeliac disease, such a condition will produce a false negative result and possibly lead to a misdiagnosis (9). 

You must be eating gluten frequently prior to your blood test for an accurate result. Do not cut it out of your diet before. For an accurate test, NICE recommends consuming gluten in more than 1 meal per day for 6 weeks prior to having the blood tests taken (8, 10).

FAECAL CALPROTECTIN

If you have IBS symptoms, you will need to have your faecal calprotectin tested (11). Faecal calprotectin is a protein released when there is inflammation in the intestines. It is directly related to bowel damage (12). 

A stool sample is taken to test faecal calprotectin levels and sent off to a laboratory for testing. 

This test can indicate inflammatory bowel disease; again, you will need further examinations should this come back positive (13).

The normal range for faecal calprotectin is <50 µg/g.

WHAT TESTS ARE NOT NEEDED FOR AN IBS DIAGNOSIS?

There are many fads to watch out for – even if you are willing to pay anything to feel ‘normal’ again. No matter how tempted you may be, please avoid the following tests to get those results safely and accurately.

ALLERGY TESTING IS NOT NEEDED IN AN IBS DIAGNOSIS

There are two types of allergies; IgE mediated and non-IgE mediated (can cause digestive symptoms). You are unable to test for non-IgE mediated allergies, so please save your money on the multiple scams available on the market.

If you have a non-IgE mediated allergy, you will need an elimination diet to get a diagnosis. You can check out our post: ‘how to get an accurate allergy test.’

STOOL TESTING

Some stool tests you see on the market can be inaccurate or provide information which is not relevant.

Online stool testing can sometimes provide misleading information. They can claim that you have ‘dysbiosis’, which doesn’t exist, seeing as we don’t know what a ‘normal’ microbiome is yet. 

Click here to read more about how accurate stool testing is.

HYDROGEN BREATH TESTING IS NO LONGER NEEDED IN AN IBS DIAGNOSIS

A hydrogen breath test involves collecting a breath sample by blowing hard into a bag intermittently and testing the quantity of hydrogen produced. Click here to read more about hydrogen breath testing. 

Previously, some doctors used hydrogen breath testing to diagnose fructose and lactose intolerance, but it is no longer considered accurate (14, 15). However, hydrogen breath testing is used for small intestinal bacterial overgrowth diagnosis (16). 

Hydrogen breath testing is not used in the diagnosis of IBS, although the symptoms of SIBO can be very similar. Read more about small intestinal bacterial overgrowth here.

WHEN ARE OTHER TESTS REQUIRED?

Depending on your symptoms, family history, age and medical history, your Doctor may require further testing.

This testing may include;

• Colonoscopies
• Endoscopies
• Ultrasound scans
• Additional blood tests

These tests rule out other conditions that your symptoms may appear to be. For example, if you have unexplained weight loss and blood in your stool, your doctor may want you to have a colonoscopy to rule out bowel cancer.

SUMMARY

We know that getting a diagnosis for your IBS may be a long-winded process. 

With all the information online it is hard to know fact from fiction. Ultimately, there is no specific test for IBS instead it is a collection of different tests to rule out other conditions. 

If you stick to the tests mentioned in this post you are more likely to get an accurate diagnosis of IBS. Please consult with your doctor and do not self-diagnose. 

It is important to get the right diagnosis to receive the right help and management for your condition. If you have any concerns, please consult with your Doctor. 

Written by Camilla Donaldson BSc Hons Nutrition (2022), reviewed by Serena Bansal Registered Dietitian BSc Hons and Kirsten Jackson Consultant Dietitian BSc Hons, RD, PG Cert