Comparison Table Of IBS Tests
Blood Tests
Test Type
Description
ACG Recommendations
When it’s typically used in IBS
1
Complete Blood Count (CBC)
An order set that contains a number of different labs like red blood cell count, hemoglobin, hematocrit, platelet count, etc.
n/a
- Yearly checkups
- IBS patients with alarm symptoms
2
Complete Metabolic Panel (CMP)
An order set that contains a number of different labs like glucose, calcium, albumin, sodium, creatinine, etc.
n/a
- Yearly checkups
- IBS patients with alarm symptoms
3
C-reactive protein (CRP)
Inflammatory marker used to test for IBD
‘We suggest that either fecal calprotectin or fecal lactoferrin and C-reactive protein be checked in patients without alarm features and with suspected IBS and diarrhea symptoms to rule out IBD.’
- Generally used in patients with diarrhea needing to rule out IBD
4
Erythrocyte Sedimentation Rate (ESR)
Inflammatory maker used to test for IBD
N/a
- Generally used in patients with diarrhea needing to rule out IBD
5
IgA anti-tissue transglutaminase and Quantitative serum IgA
Antibody testing for Celiac Disease (CD)
‘We recommend that serologic testing be performed to rule out CD in patients with IBS and diarrhea symptoms.’
- Generally used in patients who eat gluten and have diarrhea symptoms and are suspected of having CD
6
Anti-endomysial antibodies (EMA)
Antibody testing for Celiac Disease (CD)
‘We recommend that serologic testing be performed to rule out CD in patients with IBS and diarrhea symptoms.’
- Generally used in patients who eat gluten and have diarrhea symptoms and are suspected of having CD
7
HLA-DQ2/DQ8 haplotype testing
Genetic testing for Celiac Disease (CD)
N/a
Generally used in those suspected of CD who are following a GF diet and have a difficult time being diagnosed
Stool Tests
Test Type
Testing For
ACG Recommendations
When it’s typically used in IBS
8
Fecal Calprotectin and Fecal Lactoferrin
Inflammatory markers found in stool
‘We suggest that either fecal calprotectin or fecal lactoferrin and C-reactive protein be checked in patients without alarm features and with suspected IBS and diarrhea symptoms to rule out inflammatory bowel disease.’
- We recommend against routine stool testing for enteric pathogens in all patients with IBS.’
9
Enteric pathogens
The presence of a virus, bacteria, or parasites in stool
‘We recommend against routine stool testing for enteric pathogens in all patients with IBS.’
- When there is a high risk for Giardiasis, a parasitic infection
Breath Tests
Test Type
Testing For
ACG Recommendations
When it’s typically used in IBS
10
Hydrogen Lactulose and Glucose
The presence of hydrogen in specific amounts in the breath.
‘We suggest the use of breath testing (glucose or lactulose hydrogen) for the diagnosis of SIBO in patients with IBS.’
- When IBS patients are suspected of having SIBO
11
Methane
The presence of methane in specific amounts in the breath.
‘We suggest testing for methane using glucose or lactulose breath tests to diagnose the overgrowth of methane-producing organisms (IMO) in symptomatic patients with constipation.’
- When IMO is suspected in patients with constipation.
12
Lactose
The presence of hydrogen in specific amounts in the breath.
n/a
- When patients with diarrhea are suspected of having lactose intolerance or malabsorption
13
Fructose
The presence of hydrogen in specific amounts in the breath.
n/a
- When patients with diarrhea are suspected of having fructose intolerance or malabsorption
Lower Gastrointestinal Endoscopy
Test Type
Testing For
ACG Recommendations
When it’s typically used in IBS
14
Colonoscopy
IBD, microscopic colitis, colon cancer, or polyps
Recommend against routine colonoscopy in patients with IBS symptoms who are younger than 45 years old without warning signs.
- Patients who are over 45 years old and are due for a colonoscopy
- Patients who have IBS with alarm symptoms
- Patients suspected of having microscopic colitis
Anorectal Tests
Test Type
Testing For
ACG Recommendations
When it’s typically used in IBS
15
Anorectal Manometry (ARM)
Possible pelvic floor disorders by measuring the anal and rectal muscle tone and strength.
‘We suggest that anorectal physiology testing be performed in patients with IBS and symptoms suggestive of a pelvic floor disorder and/or refractory constipation not responsive to standard medical therapy.’
- When a pelvic floor disorder is suspected
- Constipation that is not responsive to treatment
16
Balloon Expulsion Test (BET)
Tests for defecatory disorders by measuring the ability to evacuate a balloon that is meant to mimic stool.
‘We suggest that anorectal physiology testing be performed in patients with IBS and symptoms suggestive of a pelvic floor disorder and/or refractory constipation not responsive to standard medical therapy.’
- When a pelvic floor disorder is suspected
- Constipation that is not responsive to treatment
17
MRI
Provides a visual on pelvic floor motion and anal sphincter anatomy to assess disordered defecation.
n/a
- When a patient has a normal BET but has symptoms that indicate disordered defecation or structural injury.
Bile Acid Malabsorption Tests
Test Type
Testing For
ACG Recommendations
When it’s typically used in IBS
18
SeHCAT
Bile acids in the body
n/a
Not available in the US.
19
Stool Testing
A 48-hour stool collection that measures total bile acids in stool
n/a
- When IBS-D patients are suspected of having bile acid malabsorption
20
Fasting serum FGF19
Bile acid malabsorption (blood test)
n/a
- When IBS-D patients are suspected of having bile acid malabsorption
21
Fasting serum C4
Bile acid production (blood test)
n/a
- When IBS-D patients are suspected of having bile acid malabsorption
Sucrase-Isomaltase Tests
Test Type
Testing For
ACG Recommendations
When it’s typically used in IBS
22
Duodenal Biopsies
Enzyme activity
n/a
- Generally used in patients with IBS-D/M or similar symptoms
- Some insurance companies require this for reimbursement for enzyme therapy.
23
Hydrogen- Methane Breath Test
The presence of hydrogen and methane in specific amounts in the breath.
n/a
- Generally used in patients with IBS-D/M or similar symptoms
- In patients who have symptoms after meals and who have not responded to a Low FODMAP diet
24
C-Sucrose Breath Test
The presence of hydrogen in specific amounts in the breath.
n/a
- Generally in patients with a IBS-D/M diagnosis or similar symptoms
- In patients who have symptoms after meals and who have not responded to a Low FODMAP diet
25
SI Genetic Testing
Presence of mutated sucrase-isomaltase genes
n/a
- Generally in patients with a IBS-D/M diagnosis or similar symptoms
- Not frequently used and is costly.
Post-Infectious IBS
Test Type
Testing For
ACG Recommendations
When it’s typically used in IBS
26
Blood test for antibodies
Increased levels of anti-CdtB and anti-vinculin which are present due to an immune response to a gastrointestinal infection.
n/a
- Used in patients with either IBS-D or IBS-M who have a history of gastroenteritis previous to their IBS diagnosis.
- Available, but not widely used as more research is needed to establish validity.
Blood Tests
- Complete Blood Count (CBC)
- Complete Metabolic Panel (CMP)
- C-Reactive Protein (CRP)
- Erythrocyte Sedimentation Rate (ESR)
- IgA anti-tissue transglutaminase (anti-tTG) + Quantitative serum IgA
- IgA Endomysial antibody (EMA)
- HLA-DQ2/DQ8 haplotype testing
Complete Blood Count (CBC)/Complete Metabolic Panel (CMP)
C-Reactive Protein (CRP) & Erythrocyte Sedimentation Rate (ESR)
Immunoglobulin A Tissue Transglutaminase (IgA TTG) & Quantitative Serum IgA
IgA Endomysial Antibody (EMA)
HLA-DQ2/DQ8 Haplotype Testing
Key Takeaways
- CBC and CMP are routine labs your doctor may order to rule out organic diseases in the presence of alarm symptoms in patients with IBS.
- CRP and ESR are inflammatory markers that are helpful in the diagnosis of IBD alongside fecal calprotectin or fecal lactoferrin.
- There are antibody tests that can help rule out Celiac Disease, but for accurate results, the tested person must be on a gluten-containing diet.
- HLA-DQ2/DQ8 are genetic tests that can help diagnose Celiac Disease in people who are not following a gluten-free diet.
Stool Tests
- Fecal calprotectin and fecal lactoferrin
- Enteric pathogens
Fecal Calprotectin & Fecal Lactoferrin
Enteric Pathogens
Key Takeaways
- Fecal calprotectin and fecal lactoferrin are inflammatory markers indicative of IBD when found in certain amounts in the stool.
- It is recommended that fCal and FL be checked with CRP (a blood test) to more accurately diagnose/rule out IBD.
- It is not recommended to test stool for enteric pathogens unless the individual is at high risk of exposure to Giardiasis.
Breath Tests
- Lactulose hydrogen breath test
- Glucose hydrogen breath test
- Methane breath test
- Lactose breath test
- Fructose breath test
Lactulose Hydrogen Breath Test
Glucose Hydrogen Breath Test
Methane Breath Test
Lactose Breath Test
Fructose Breath Test
Key Takeaways
- Breath tests involve the ingestion of a specific carbohydrate dose followed by measuring exhaled gas over several hours.
- The ACG recommends lactulose and glucose hydrogen breath tests in diagnosing SIBO despite the possibility of false positives.
- The ACG recommends the methane breath test in patients with constipation.
- Carbohydrate malabsorption or intolerance may play a part in exacerbating IBS symptoms or could be the origin of symptoms.
- There are no guidelines in using breath tests for carbohydrate malabsorption or intolerance in IBS patients at this time.
- Reducing the amount of lactose or fructose in the diet or trialing a low FODMAP diet under the guidance of a registered dietitian is a way to seek symptom improvement without a breath test that may give inaccurate results.
Lower GI Endoscopy
Colonoscopy
Key Takeaways
- A colonoscopy is not needed in all IBS patients
- IBS patients who may require a colonoscopy include patients who are over 45 years old and are due for a colonoscopy, patients who have IBS with alarm symptoms, and patients suspected of having microscopic colitis.
Anorectal Testing
- Anorectal manometry (ARM)
- Balloon expulsion test (BET)
- Evacuation imaging via MRI
ARM
BET
MRI
Key Takeaways
- Anorectal disorders share symptoms with IBS and may overlap
- The ACG suggests anorectal testing in patients with IBS whose symptoms suggest pelvic floor disorders and patients with constipation that do not respond to standard treatment.
- Tests used to diagnose anorectal disorders include an anorectal manometry (ARM), the balloon expulsion test (BET), and an MRI.
- ARM and BET involve a balloon being inserted into the rectum and taking different measurements.
- MRIs give an image of the pelvic area and can help confirm structural injuries or pelvic floor disorders.
Bile Acid Malabsorption
- Selenium (Se)-homocholic acid taurine (SeHCAT)
- Stool testing in BAM
- Blood testing in BAM
SeHCAT
Stool Testing
Blood Testing
- Fibroblast growth factor 19 (FGF19): is involved in decreasing bile acid synthesis, and a low fasting serum level may indicate BAM20.
- Serum C4 is a direct measure of bile acid production. A higher level is indicative of BAM and has been seen in patients with IBS-D in comparison to those with IBS-C or healthy people20.
Key Takeaways
- Bile acid malabsorption can contribute to symptoms in some IBS-D patients.
- Stool testing for bile acids is the most reliable test available in the US.
- Blood tests for bile acid malabsorption are available and may help diagnose BAM, but access is limited.
Sucrase-Isomaltase Deficiency
- Duodenal Biopsies
- Hydrogen Methane Breath Test
- C-Sucrose Breath Test
- Sucrase-Isomaltase (SI) Genetic Test
Duodenal Biopsies
Hydrogen Methane Breath Test
13C-Sucrose Breath Test
SI Genetic Test
Key Takeaways
- Sucrase-isomaltase deficiency (SID) makes it difficult to digest sucrose and some starches.
- Testing for SID is imperfect, with some tests being costly and others being invalidated.
- A duodenal biopsy is the gold standard for diagnosing SID, but is costly and invasive.
- The sucrose dose required for the hydrogen-methane breath test can often cause symptoms in people with SID.
- The 13C-Sucrose breath test is a better tolerated breath test, but is not validated.
- Genetic testing for SID is available but cannot capture the acquired version of SID or genetic variations that have not been identified.
Post-Infectious IBS
There are two antibody tests that are being studied as potential IBS biomarkers for post-infectious IBS. Now when you hear the word ‘antibody’ think of your immune system sending out a defensive line (aka antibodies) to fight off something that’s been deemed a threat. The antibodies being researched are:
- Anti-cytolethal distending toxin B (anti-CdtB)
- Anti-vinculin
Anti-cytolethal Distending Toxin B (anti-CdtB) & Anti-vinculin
Key Takeaways
- There are two antibodies being researched as potential biomarkers in people with post-infectious IBS (PI-IBS) called anti-cytolethal distending toxin B (anti-CdtB) and anti-vinculin.
- The research conducted has shown mixed results, and additional research is needed before these tests can be recommended as legitimate biomarkers for PI-IBS.
Allergy Tests
Key Takeaways
- People with IBS have more adverse reactions to food than the general population but do not have a higher rate of true food allergies.
- The ACG only recommends that patients with IBS get food allergy tests if there are reproducible symptoms when eating specific foods.
- Allergy tests have a low specificity, which could give a high rate of false positives.
- Tests for sensitivities or intolerances, like the serum IgG test, have not been validated and are not clinically recommended.
Intestinal Permeability Tests
Increased intestinal permeability (sometimes referred to as ‘leaky gut’) has been identified in certain IBS populations, but the scientific community is still trying to sort out if permeability changes are a cause or consequence of the underlying disease state.
Currently, the ACG has no recommendations for testing intestinal permeability in clinical practice for IBS management.
At this time, we do not recommend permeability testing for several reasons, including:
- A lack of standardized testing methods
- A lack of standardized normative testing values – i.e., values which determine the degree of permeability that’s normal or pathological
- The cost, potential invasiveness, impracticality, or time intensiveness of the tests
- A lack of well-validated treatment options for increased permeability
- Sparse evidence that intestinal permeability improvements alter the underlying disease state or symptoms
We’re giving permeability testing a brief mention here because, although far from perfect, they have been widely used in IBS populations in scientific literature and research. We will review both orally ingested probes and common blood tests that are thought to measure permeability. And while we don’t recommend these tests just yet, this is an evolving area of research that may someday bring new therapeutic options to the table for IBS management. In the meantime, any permeability test results should be interpreted with caution.
Orally Ingested Probes
Blood Tests
Key Takeaways
- Gut permeability testing has been used in scientific literature and research, but these tests have yet to be fully standardized and validated.
- Commonly used tests include orally ingested probes that are taken by mouth and later measured in the urine, as well as several types of blood tests
- Based on the research available, we don’t currently recommend permeability testing and any test results should be interpreted with caution.