How is Irritable Bowel Syndrome Diagnosed?

How is Irritable Bowel Syndrome diagnosed?

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that causes a wide range of gut symptoms, such as abdominal pain, bloating, excess wind/flatulence, and changes in bowel habit (diarrhoea, constipation, or both) without any signs of damage or disease in the digestive tract. Getting a diagnosis of a chronic medical condition can be challenging.

This article to going to walk you through the diagnosis process and will cover:

• What are the Rome IV criteria for diagnosing IBS?
• What are red flag symptoms?
• What other symptoms do doctors look for?
• What medical tests are used to diagnose IBS?
• What medical tests are generally not necessary when diagnosing IBS?
• Are there any tests that help diagnose intolerance to certain FODMAP groups?
• Are there other food intolerance tests that can be used?
• Are there any tests that should be avoided when diagnosing food intolerances?

Let’s get started. Understanding what symptoms the doctors are looking for and what medical tests are available, is the first step in getting a diagnosis for IBS.

Irritable bowel syndrome can be diagnosed using a combination of the Rome IV criteria, and through ruling out other gastrointestinal disorders like inflammatory bowel disease, coeliac disease and bowel cancer.

What are the Rome IV criteria?

The Rome IV is a set of criteria that most IBS patients have in common. According to IBS experts, the Rome criteria is considered to be 98% accurate at identifying patients with IBS (1).

The criteria are:

Recurrent abdominal pain, on average, at least 1 day per week in the last 3 months, associated with 2 or more of the following criteria:

1. Related to defecation
2. Associated with a change in frequency of stool (e.g. passing bowel movements multiple times per day OR having long periods of time between bowel movements)
3. Associated with a change in form (appearance) of stool ( e.g. are the stools liquid or soft, or lumpy or hard lumps, or a mixture)

If you have been presenting with abdominal pain, bloating, and change in bowel habit your doctor will decide if you match the Rome IV Criteria listed above and will discuss red flag symptoms.

What are red flag symptoms?

Red flag symptoms indicate that there could be other serious medical conditions that need to be ruled out before diagnosing you with IBS (3 4). Additional medical tests will be used to rule out other medical conditions linked to red flag symptoms.

Red flag symptoms include:

• unintentional and unexplained weight loss
• rectal bleeding
• a family history of bowel or ovarian cancer, inflammatory bowel disease, coeliac disease
• onset of symptoms in patients aged greater than 50 years (over 60 years in the NICE guideline)
• nocturnal symptoms, e.g. waking from sleep with pain or the need to pass a bowel motion
• anaemia (low iron levels)
• abdominal masses
• rectal masses
• inflammatory markers for inflammatory bowel disease

(3; 4)

 

What other symptoms do the doctors look for?

To be diagnosed with IBS, your abdominal pain and discomfort need to be related to passing a bowel motion (defecation) or associated with altered bowel frequency or stool form (4).

You should also have at least two to four of the following symptoms:

• abdominal bloating (more common in women than men), distension, tension or hardness
• altered stool passage (straining, urgency, incomplete evacuation)
• symptoms made worse by eating
• passage of mucus
• the feeling of incomplete emptying

(3; 4)

You may or may not also experience symptoms that include feeling constantly tired (lethargy), nausea, backache and bladder symptoms, as these are also common in people with IBS  (3; 4).

 

What medical tests are used to help diagnose IBS? 

Before your doctor is able to diagnose you with IBS it is important to do the following blood tests to rule out other diagnoses:

• full blood count (FBC)
• erythrocyte (red blood cell) sedimentation rate (ESR) or plasma viscosity
• c‑reactive protein (CRP)
• thyroid function test (TSH) (Some thyroid issues can cause gut symptoms)
• antibody testing for coeliac disease (deaminated Gliadin [DGP] and tissue transglutaminase [TTG]).

(3; 4)

What medical tests are generally not necessary when diagnosing IBS?

Unless you have red flag symptoms, there is often no need for additional medical tests. Your doctor is the best person to advise based on your situation if any of the following are necessary:

• ultrasound
• rigid/flexible sigmoidoscopy
• colonoscopy
• barium enema
• gastroscopy
• faecal ova and parasite test (if you have been overseas, please ask for this test)
• faecal occult blood
• hydrogen breath test (for lactose intolerance and bacterial overgrowth) (4).

If your doctor is concerned about your symptoms, he/she will refer you to a gastroenterologist. A gastroenterologist is a specialised medical physician who specialises in diagnosing and treating diseases of the gastrointestinal tract and liver (5).

 

Are there any tests that help diagnose intolerance to certain FODMAP groups?

If you have been diagnosed with Irritable Bowel Syndrome (IBS), your medical practitioner might recommend seeing a dietitian to determine if trialling the low FODMAP diet or other dietary intervention is suitable.

If the low FODMAP diet is recommended, they will place you on a strict low FODMAP diet for 2 to 8 weeks (6). Your dietitian will then review your progress and help you test the different FODMAP groups (6). Then can then advise you on which foods and how much you can re-introduce into your diet. This method is the most effective way to test your tolerance levels to all of the FODMAP groups.

Some doctors might recommend breath tests to identify if you malabsorb lactose, fructose, or sorbitol. These tests work by measuring the amount of gas (hydrogen and/or methane) in your breath after consuming one of the FODMAP sugars (6 7). In theory, if there is a significant rise in one or both of these gases then it can be confirmed that you malabsorb that particular FODMAP sugar (6 7). However, research highlights that these test results may be inaccurate (9 10). These tests can show both false positive or negative results, which means a positive breath test may not mean you will have issues digesting the sugar (9).

The most reliable way to diagnose which FODMAP groups trigger your gut symptoms is through the low FODMAP diet process (ideally with the guidance of a FODMAP trained dietitian).

 

Are there other food intolerance tests that can be used?

Your doctor might use IgE blood test or skin prick tests to check if you have a food allergy (11). A food allergy is where you have an immune system response to consuming certain foods (11). These tests are unlikely to show if you have food intolerances (this is where your body reacts to a certain food but it is not related to an immune system response).

Are there any tests that should be avoided when diagnosing food intolerances?

Many food intolerance tests on the market lack sufficient scientific evidence and are not good diagnostic tools for diagnosing food intolerances.

Here are some of the tests that are not recommended by medical professionals:

IgG blood tests (IgG4, York Test, IgG RAST/ELISA Testing). These blood tests look at IgG antibodies present in the blood, and test results claim that if there is an increase in IgG antibodies to a certain food then that indicates a food intolerance (11 12 13). There is no strong evidence supporting this theory (11 12).

Kinesiology is based on the belief that when you are intolerant to a food it creates an energy imbalance, which can be identified through muscle testing (11). There is no strong evidence supporting this theory (11 12).

Hair analysis/testing is when hair is sent to the laboratory and energy fields are scanned to look for imbalances (11). This is an unproven method of allergy and food intolerance testing and has no scientific basis (11 12).

Electrodermal (Vega) test measure the electromagnetic conductivity in the body with the belief that if you are intolerant to a food it will cause a dip in the electromagnetic conductivity (11). Research studies show that this test is not scientifically valid (11 12).

Final Thoughts

Please talk to your doctor if you are concerned that you have IBS. Your doctor will be able to determine if IBS or another medical condition is contributing to your symptoms. You and your doctor can then discuss treatment options and food intolerance testing to help you manage your symptoms.

Image credit: Alexander Raths/Shutterstock.com