What Can Be Detected In A Stool Sample?

Why is poo a taboo? 

Have you ever been asked to give a stool sample? Would you find this easy?

For many members of the public, being asked to give a stool sample could be a highly embarrassing affair. Why? Quite literally - it stinks! People aren’t so enthusiastic about handling their waste because poo is perceived as ‘dirty’ or ‘embarrassing’.1 Moreover, the mere fact that you have to physically give the container to a GP surgery receptionist, clearly marked as a ‘poo sample’, can hinder the willingness of a person to do so for fear of judgment. 

However, to healthcare professionals, such as doctors and nurses, a stool sample is a world of information and is extremely valuable for understanding many disease states. 

Poo is something all humans have in common, (and animals too!). So how do we encourage people to participate in stool sampling? One study found that a clear explanation of the ‘why’ give the sample increased people’s engagement in stool sampling.1

It is common knowledge that stool sampling is highly important in the early detection of colorectal cancer.2 Screening programmes involving stool sampling are widely used in the US and the UK. This is a way of detecting cancer when there are no apparent symptoms. The narrative around colorectal cancer is of such great importance in informing the public why ‘picking up their poo’ is beneficial, that people have dedicated much time to the cause. Sadly, one of the biggest advocates of colon cancer awareness in the UK, Dame Deborah James, has recently passed away at the age of 40. She spent years trying to increase the public’s awareness of cancer and break taboos surrounding the topic of ‘poo’. She truly showed the British public, as well as the worldwide audience, that it was important to talk about poo.3 

What is a stool sample?

To demystify the ‘stool sample’, let’s look at what poo is. 

Faeces, known as poo or stools, contain:

  • Water
  • Protein
  • Fats
  • Polysaccharides (fibre)
  • Bacteria (both dead and alive)
  • Ash
  • Undigested food residues 4

The percentage content of these substances depends on a person’s diet. Your poo is made of the things you eat, as well as some extra substances that the body puts there. 

Why is stool testing done?

There are many reasons why doctors ask us to perform this rather bizarre task. The sample may be used to diagnose a health condition or rule out a disease. The sample may also be used to find out what is happening in your digestive system by looking at the bacteria that live there.5

Types of stool test

There are several different stool tests, the most common are described below: 4, 5, 6

  • Faecal Occult Blood test - used in colorectal cancer screening to identify blood in your poo.
  • Faecal Immunochemical test - also used to detect blood in your poo as part of colorectal cancer screening.
  • Faecal Calprotectin - a protein found in stools when the gut is inflamed. 
  • Stool Culture - used to identify bacteria or parasites that might be making you acutely unwell. This test is used to detect H. Pylori, a common bacteria causing stomach ulcers. 

What are stool samples used for?

Some common conditions that involve stool sampling as a part of diagnosis: 7

  • Inflammatory bowel disease - Crohn’s disease or ulcerative colitis are both conditions where there is inflammation of the wall of the gut.
  • Gastroenteritis - diarrhoea and vomiting usually caused by a stomach bug. 
  • Cancer - colorectal cancer (cancer of the digestive tract).

Tests for infection

Acute gastroenteritis, or an infection, can be caused by a variety of viruses and bacteria. Quite often, the situation resolves by itself, but when the condition worsens, it becomes important to identify the bacteria - often referred to as pathogenic bacteria.8 When the diarrhoea is accompanied by fever, sweating, bloody stools or evidence of dehydration, then stool sampling is needed to help diagnosis and corresponding treatment. Not only is testing important for the patient, but it is also an essential part of monitoring possible outbreaks. 

The main offending bacteria that require a patient to be monitored with the above symptoms are:

  • E.Coli
  • Shigella
  • Campylobacter
  • Salmonella
  • Clostridium Difficile

After your doctor gets the stool sample results, the bacteria can be identified, and the treatment plan can be finalised. This could involve antibiotics or close monitoring for a while. The most effective way to prevent infections such as these is to adopt excellent handwashing skills after going to the bathroom. If you are acutely unwell, with diarrhoea lasting longer than a day, it is important to wash your hand carefully before handling food or touching other people. Public health guidelines recommend that people who work closely with food should not go to work with these symptoms as to prevent food contamination, which is a way these pathogenic bacteria can be passed on.8 

Tests for inflammatory bowel disease

Patients with Chron’s disease and ulcerative colitis require ongoing disease monitoring so the correct treatment can be given. Monitoring patients can help doctors identify people at risk of a relapse. If these patients are identified early, there is a chance of staying in remission, and they may be less likely to have irreversible bowel surgery.9 

There are different ways to monitor these inflammatory conditions. Endoscopy is one, however, it is costly and invasive. If faecal calprotectin, a protein found in stools, is detected in the bowel, it is directly related to a period of inflammation. Therefore,  it is a stable marker in inflammatory bowel disease status, which can be tested by analysing a stool sample in the laboratory.9 

Tests for colon cancer

Colon cancer, also known as colorectal cancer, is the cause of 10% of cancer deaths in western countries.10 In the 1950s, it was not a common type of cancer, and its increased incidence today is thought to be due to obesity, smoking, limited exercise and poor diet.10 Screening for this cancer is extremely important. It is predicted that early detection through screening will have a major impact on its detection over the next 15 years. This, however, can only happen if patients are willing to be screened. 

The main symptoms of this disease are:

  • Blood in stools
  • Change in bowel habits
  • Abdominal pain

The main tests for colorectal cancer early detections are the faecal occult blood test (gFOBT) or Faecal immunochemical Test (FIT). These detect the presence of blood in faeces through a chemical reaction. They are widely available and relatively cheap to carry out. In one study in the United States, it was found that yearly gFOBT tests on dried stool samples, in people between the ages of 50-80, reduced the number of deaths in this group over 13 years by 33%.6 

Tests for fat malabsorption

Fats from our food are broken down and absorbed into the bloodstream throughout the process of digestion. The majority of fats are digested in the small intestine by a cocktail of naturally occurring substances. When the process of absorbing fat is affected in the gut, this can lead to lower than necessary amounts being absorbed into the blood. Fats are an essential part of our diet, and when we do not get enough, this can lead to feeling unwell, losing weight and experiencing gastric disturbances like bloating, diarrhoea and foul-smelling stools.11

Stool sampling is important to detect malabsorption. Quite literally, the fat levels are measured in a singular stool sample. If this is positive then the gold standard test, 72-hour faecal fat excretion analysis is carried out. This involves eating a specified amount of fat before carrying out the test.11

Tests for Helicobacter (abdominal pain)

Helicobacter pylori are one of the many bacteria that live in our digestive tract or gut. This bacteria is adapted to the inhospitable acidic environment in your stomach. Although you may not experience direct symptoms of this infection, it can eventually lead to gastritis and gastric ulcers if undetected.12 Gastritis is an inflammation of the stomach, and a gastric ulcer is a painful sore in the stomach lining. 

Tests for H.Pylori are important when experiencing gastric discomfort as, if not treated, it can lead to ulceration. There are different ways to test for H.Pylori, one of which is a stool antigen test. This test is effective in both detecting an active infection and also seeing if the bacteria has been eradicated.12

Procedure

Collecting the stool sample

Your healthcare professional will explain how to collect the stool sample. 

The process is usually as follows:7

  • Write your name, date of birth and on the label of the collecting sample bottle.
  • Now it is time to catch the poo. To do this you must place something in the toilet to catch it. This can be a plastic food container or some plastic placed across the rim of the toilet seat. 
  • The poo cannot touch the inside of the toilet. This could lead to contamination. 
  • The spoon or spatula that is part of the kit should now be used to collect a piece of the poo. After placing the poo in the collection bottle it should then be screwed shut.
  • If you are using a container that has been given to you by the doctor, you should try to fill a third of it. 
  • Any material or implement you use to collect your poo should then be put in a plastic bag, wrapped up and put in the bin. If you are concerned about smells, then best to empty your kitchen or bathroom bin into the main bin on the outside of your house.
  • And finally, make sure you wash your hands thoroughly with soap and warm water when finished. You can find good handwashing techniques here if you would like to ensure you are doing it thoroughly.13 

There are a few things that should be kept in mind when collecting your sample:7

  • Try not to collect any pee in the sample. If you do, then don’t fret as a little is ok. 
  • If you do need to pee, then try to do this first before you collect your poo. 
  • It is acceptable to use plastic gloves when collecting your sample, as long as they are put in a bag and then in the bin when you are finished. 

Required sample size

As mentioned above, the sample size should be one-third of your container or the size of a walnut.7

Storage

It is essential that the stool sample is fresh and, therefore, should be handed in immediately. If it isn’t fresh, the bacteria can multiply and this can affect the accuracy of your result. Your doctor will tell you if the sample can be kept in the fridge if you are unable to hand it over quickly. If it has to be kept in the fridge, it must be put in a sealed plastic bag first.7  

How is stool sample testing done?

There are three main ways stool sample testing is carried out: 14

  • Macroscopic Examination - looking at a fresh stool sample in the lab and comparing it against charts used to diagnose disease. The main aspects examined are colour, consistency, form, presence of mucus, quantity and smell. 
  • Microscopic Examination - the stool is examined under a microscope as the presence of some specific signs of disease can only be seen this way (e.g. white blood cells). 
  • Laboratory testing - the stool sample is tested using substances or processes in the lab to observe reactions that show signs of disease or infection. 

Getting the results

What do the results mean?

In a stool culture, used to detect bacteria, the result may say ‘isolated’ which means a particular bacteria was found. It may say ‘not isolated’ which means it was tested for some time and no pathogenic bacteria was found.5 

If your gFOBT or FIT returns positive for blood then a follow-up colonoscopy (a camera inside the intestine) will be carried out to see where the blood is coming from.15 These tests do not diagnose cancer on their own, your doctor will request further investigations. Blood in the stools can happen for many reasons, this is why more procedures and tests must be carried out.14

Stool sample testing in children

Much like adults, poo samples are really important in diagnosing conditions in children. One of the main reasons your child’s stool would be tested is if they experience diarrhoea. However, conditions such as malabsorption and inflammation of the intestine can also be tested for using stool samples.16 

The major difference in getting a stool sample from a child compared with adults is that someone will need to collect it for them. Some infants are too young to even tell their caregivers of when poo is going to happen. So how can you collect a stool sample from your child?16

  • Wear gloves - if your child has diarrhoea, the process could get messy.
  • A hat-shaped plastic lid can be used to collect the stool sample. This can be placed at the child’s rear when passing poo, or placed in the toilet to catch it.
  • N.B. A stool sample CANNOT be taken out of the toilet bowl after your child has finished their poo, this increases the risk of contamination. 
  • Like an adult sample, the child’s sample should be collected in a clean plastic container with a screw top, their name must be written clearly on the label.
  • The healthcare professional requesting the sample should give you instructions.
  • If you are unsure how to do this or have any questions, do not hesitate to contact your nurse or doctor.

Finally, when the requested tests to ben carried out, you will receive the results and they will be further discussed with the child’s physician. 

Limitations of stool sample testing

Irritable bowel syndrome, or IBS, is a chronic gastrointestinal disorder. It is among the world's most commonly diagnosed gut issues.17 People with this condition are usually divided into those who have chronic diarrhoea or chronic constipation. Although IBS is a the disease of the gut, doctors do not normally use stool samples to test for it. Rather, they will order stool testing to rule out other underlying conditions such as inflammatory bowel diseases or cancer.18

Like any diagnostic test, stool sampling is not 100% accurate in determining a diagnosis for the first time.19 This is why doctors will often request more than one test together or follow-up tests. Healthcare professionals are trained in understanding the accuracy of different tests in diagnosis, therefore, they will make the best choice regarding the tests you need.19 

Summary

Stool samples have long been considered embarrassing or dirty to many people.1 However, for healthcare workers, these samples are extremely important in detecting diseases such as colorectal cancer or bacterial infections. The stool sample is a piece of your poo collected using a special kit given to you by your doctor..7 

There are different types of stool tests and not all are discussed in this article. However, the most common you may hear of are faecal occult blood test (gFOBT), faecal immunochemical test (FIT), faecal calprotectin test, and stool cultures. These tests are mainly involved in the diagnosis of illnesses such as colorectal cancer, bacterial infection (e.g. H. Pylori), inflammatory bowel diseases and malabsorption syndrome.6, 8, 9, 10, 11 Your poo is tested by qualified healthcare professionals. They examine a fresh poo sample against charts to detect abnormalities, in a laboratory under the microscope or with chemical testing.14 

A bacterial infection can show up as positive or negative for a specific bacteria. With regards to colon cancer, the gFOBT and FIT can come back as positive for blood in the stool, however, these tests do not diagnose cancer alone. Further investigation will always be ordered by your doctor.5, 14, 15 

Children and infants may also need to have stool sampling tests done. The major difference in this process for them is the fact someone needs to collect it for them, usually their caregivers. The person in charge of your child's medical care will advise you on how best to do it and why a stool sample is being requested of them.16 

All in all, research has shown that providing stool samples when asked can prolong your life, especially when you reach the age of 50-80. Evidence also suggests that colon cancer incidence is on the increase in Western countries.6 It is therefore more important than ever, that we take away the taboo about poo. 

References

  1. Lecky DM, Hawking MK, McNulty CA; ESBL steering group. Patients' perspectives on providing a stool sample to their GP: a qualitative study. Br J Gen Pract. 2014 Nov;64(628):e684-93. 
  2. Center for Disease Control and Prevention. Colorectal (Colon) Cancer. 2022 [8th July 2022]. Available from:https://www.cdc.gov/cancer/colorectal/basic_info/screening/index.htm
  3. BBC News.Dame Deborah James: Cancer campaigner dies aged 40. 2022 [7th July 2022]. Available from: Dame Deborah James: Cancer campaigner dies aged 40 - BBC News
  4. Rose C, Parker A, Jefferson B, Cartmell E. The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology. Crit Rev Environ Sci Technol. 2015 Sep 2;45(17):1827-1879. 
  5. The Association of Clinical Biochemistry and Laboratory Medicine- Lab Tests Online UK. Stool Culture. 2019 [7th July 2022]. Available from: Stool Culture (labtestsonline.org.uk)
  6. Issa IA, Noureddine M. Colorectal cancer screening: An updated review of the available options. World J Gastroenterol. 2017 Jul 28;23(28):5086-5096.
  7. NHS UK. How should I collect and store a poo (stool) sample? 2019 [7th July 2022]. Available from: How should I collect and store a poo (stool) sample? - NHS (www.nhs.uk)
  8. Hatchette TF, Farina D. Infectious diarrhoea: when to test and when to treat. CMAJ. 2011 Feb 22;183(3):339-44. 
  9. Chang S, Malter L, Hudesman D. Disease monitoring in inflammatory bowel disease. World J Gastroenterol. 2015 Oct 28;21(40):11246-59. 
  10. Kuipers EJ, Grady WM, Lieberman D, Seufferlein T, Sung JJ, Boelens PG, et al Colorectal cancer. Nat Rev Dis Primers. 2015 Nov 5;1:15065. 
  11. Zuvarox, Tyesha, and Chris Belletieri. ‘Malabsorption Syndromes’. StatPearls, StatPearls Publishing, 2022. 
  12. Diaconu S, Predescu A, Moldoveanu A, Pop CS, Fierbințeanu-Braticevici C. Helicobacter pylori infection: old and new. J Med Life. 2017 Apr-Jun;10(2):112-117. 
  13. NHS UK. How to wash your hands. 2019 [6th July 2022]. Available from: How to wash your hands - NHS (www.nhs.uk)
  14. Kasırga E. The importance of stool tests in diagnosis and follow-up of gastrointestinal disorders in children. Turk Pediatri Ars. 2019 Sep 25;54(3):141-148.
  15.  National Library of Medicine Medline Plus. Fecal Immunochemical Test (FIT). 2021 [6th July 2022]. Available from:  Fecal immunochemical test (FIT): MedlinePlus Medical Encyclopedia
  16. Kids Health. Johns Hopkins All Children’s Hospital :Stool Tests. 1995-2022. [7th July 2022]. Available from: Stool Tests - Johns Hopkins All Children's Hospital (hopkinsallchildrens.org)
  17. Saha L. Irritable bowel syndrome: pathogenesis, diagnosis, treatment, and evidence-based medicine. World J Gastroenterol. 2014 Jun 14;20(22):6759-73. 
  18. National Institute of Diabetes and Digestive And Kidney Diseases. Diagnosis of Irritable Bowel Syndrome. 2017 {7th July 2022]. Available from: Diagnosis of Irritable Bowel Syndrome | NIDDK (nih.gov)
  19. Shreffler, Jacob, and Martin R. Huecker. ‘Diagnostic Testing Accuracy: Sensitivity, Specificity, Predictive Values and Likelihood Ratios’. StatPearls, StatPearls Publishing, 2022. 

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Danielle Ferrie

Masters of Pharmacy - MPharm, University of Strathclyde, Scotland

Danielle is a Locum Pharmacist with strong business acumen having exposure to clinical and management roles between the hospital and community sectors.
She has 8 years of experience as a GPhC registered Pharmacist, and 6 years as an EFL Teacher working with University lecturers on editing articles.
She is currently undertaking the "Writing in the Sciences" online from Stanford.

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