How many days can feces be stored for analysis in the refrigerator: rules and terms

Stool testing is a standard procedure for diagnosing gastrointestinal diseases, parasitic infections or assessing intestinal microflora. But what to do if the material was collected only in the evening, and the laboratory works in the morning? Can feces be stored in the refrigerator, and if so, for how many days? The answer depends on the type of research, storage conditions and even on the specific laboratory.

In this article we will analyze exact storage periods for feces for different tests (coprogram, for worm eggs, PCR, dysbacteriosis), we will tell you how to properly collect and store the material so as not to distort the results. You will also learn what mistakes patients most often make and how to avoid them. Important: the rules may differ depending on the research methods requirements of the laboratory - always check them when you sign up for analysis.

Why the storage periods for feces are limited

Stool is a biological material, which begins to decompose immediately after defecation. Bacteria actively multiply in it, pH changes, enzymes and cells are destroyed. If you store feces for too long, even in the refrigerator:

• 🦠 The microflora is distorted: some bacteria die, others multiply, which leads to false test results for dysbiosis.
• 🔬 Enzymes are destroyed: for example, elastase-1 (a marker of the pancreas) loses activity after 6-8 hours.
• 🐛 Parasitic eggs are deformed: during long-term storage, their shell may become fragile, and the laboratory technician will not detect them.
• 🧬 DNA degrades: for PCR tests this is critical - the sensitivity of the test falls.

Laboratories usually indicate the maximum shelf life of stool - from 2–3 hours up to 2 days, but this depends on the type of study. For example, for coprograms it is permissible to store material for up to 8–12 hours, and for analysis for hidden blood no more than 6 hours.

Stool shelf life for different tests

Below is a table with the recommended storage time for stool in the refrigerator (+2...+8°C) for the most common studies. Please note: some laboratories may have stricter requirements - always check them on the website or by phone.

For bacteriological culture (detection of pathogens like Salmonella or Shigella) stool must be delivered to the laboratory within 1–2 hours. In exceptional cases, storage up to 6 hours is allowed, but only in special preservatives (for example, Stuart's medium or glycerin buffer).

How to properly store feces in the refrigerator

Even if you met the acceptable deadlines, improper storage can distort the results. Follow these rules:

1. Use a sterile container. It is best to use pharmaceutical plastic containers with a spoon-spatula. Baby food or mayonnaise jars are not suitable, even if they are used. wash.
2. Close the lid tightlyFeces should not come into contact with air - this accelerates oxidation and decomposition.
3. Temperature: +2...+8°CStore the container on the middle shelf of the refrigerator (not in the door or in the refrigerator). freezer!). The temperature in the door is unstable, and freezing destroys cells and DNA.
4. Do not mix. portionsIf you collect feces during the day (for example, to test for worm eggs), store each portion separately.

For tests for occult blood or calprotectin some laboratories provide containers with a preservative. In this case:

• 🧪 Immediately after collecting the feces, place it in a preservative and mix.
• ⏳ The shelf life increases to 24–48 hours (check the instructions for the preservative).

⚠️ Attention: If you store feces for analysis on rotavirus infection or norovirus, use only containers without preservatives. These viruses are sensitive to chemical additives, and the result may be different. false negative.

What should not be done when storing feces

Some actions completely distort the results of the analysis:

• 🚫 Store at room temperature longer than 1–2 hours. At +20°C, bacteria multiply 2–3 times faster than in the refrigerator.
• 🚫 Freeze stool. Cells, enzymes and DNA are destroyed, with the exception of special tests (for example, on caliciviruses). storage at −20°C in a transport environment is allowed.
• 🚫 Use unsealed containers. Feces dry out, and pathogens die from contact with oxygen.
• 🚫 Collect stool after an enema or laxatives. This distorts the microflora and consistency.
• 🚫 Store stool in the freezer for longer than 24 hours. hours, even if the laboratory allows it. Repeated defrosting/freezing destroys the structure of the material.

Errors are especially critical for tests on parasites i infections. For example, when searching giardia stool should be as fresh as possible - the parasite cysts are destroyed after 6-8 hours, even in the refrigerator. For accuracy, sometimes you need to donate. data-i="154">(within 30–60 minutes after defecation). warm feces (within 30–60 minutes after bowel movement).

Why not use matchbox for storage?

In cardboard boxes, feces quickly dry out, and microorganisms die due to lack of moisture. In addition, the cardboard can absorb liquid, which will distort the consistency of the sample. Laboratories refuse to accept material in non-sterile containers.

How to collect stool for analysis: step-by-step instructions

Correct collection of stool is the key to an accurate result. Follow this algorithm:

1. Preparation:
   • 🚽 2-3 days before collection, exclude foods that color feces (beets, blueberries, activated carbon).
   • 💊 Stop taking antibiotics, probiotics and laxatives (if this does not contradict the prescription doctor).
   • 🧼 Wash with warm water and soap before defecation.
2. Collecting material:
   • 🧻 Use a clean, dry container (pot, vessel or disposable plate). Do not take feces from the toilet!
   • 🥄 Take 3-4 portions from different parts of the feces (top, bottom, middle) with a sterile spoon.
   • 📦 Place about 1-2 teaspoons of feces (5-10 g) in the container.
3. Storage and transportation:
   • ❄️ Immediately close the container and place in the refrigerator.
   • 🚗 Deliver to the laboratory in a cooler bag or thermal bag with cold elements.

For analysis occult blood 3 days before collection, exclude meat, fish, liver and green vegetables (they contain peroxidase, which gives a false positive result). To test for carbohydrates (in infants), stool must be liquid - collect it immediately after defecation in a sterile tube.

⚠️ Attention: If you are donating feces for PCR to detect Clostridioides difficile (the causative agent of pseudomembranous colitis), it cannot be stored for longer than 2 hours without a special preservative. This microorganism quickly degrades.

What to do if you don’t have time to donate feces on time

There are different situations: the laboratory is closed for the weekend, there is no transport, or you simply didn’t have time. Here's what you can do:

• 📞 Call the laboratory. Some private clinics accept stool on weekends or extend the shelf life by using preservatives.
• 🧊 Use transport medium. For example, UTM environment or saline (check with the laboratory).
• ⏳ Collect a new portionis suitable for PCR analyses. If more than 24 hours have passed, it is better to repeat the collection - the results of the old sample will be unreliable.
• 🏥 Contact another laboratory. Some networks (for example, Invitro, Helix) have collection points with extended opening hours.

If you store stool longer permissible period warn the laboratory —they can make a note on the referral form. In some cases, laboratory technicians take storage time into account when interpreting results (for example, for a coprogram).

Frequently asked questions about storing feces for analysis

Is it possible to store feces in the freezer?

No, freezing destroys the structure of feces, enzymes and DNA. An exception is some virological studies (for example, on norovirus), where storage at −20°C in a transport environment is allowed for no longer than 7 days. But for routine tests (coprogram, worm eggs), freezing is unacceptable.

What happens if feces were stored longer than the permitted period?

The consequences depend on the type of analysis:

• 🔬 Coprogram: distortion of fatty acids, muscle fibers, leukocytes.
• 🦠 Dysbacteriosis: false decrease in the number of bifidobacteria and increase in opportunistic flora.
• 🩸 Occult blood: false positive result due to hemolysis erythrocytes.
• 🧬 PCR: decreased sensitivity of the test (viruses/bacteria may not be detected).

The laboratory may refuse to accept such material or make a note about the unreliability of the results.

Is it possible to collect stool in the evening if the analysis is in the morning?

Yes, but only for certain studies:

• ✅ Coprogram: can be stored for up to 8-12 hours in the refrigerator.
• ✅ Eggs of worms: up to 24 hours (preferably up to 12).
• ❌ Dysbacteriosis: only if the laboratory allows (usually no more than 2-6 hours).
• ❌ Hidden blood: maximum 4-6 hours.

Check the requirements with your laboratory - some private clinics allow longer storage when using preservatives.

Do you need to donate stool in a special container?

Yes, pharmacy containers are sterile and sealed. Alternatives:

• 🧪 Glass jars with a screw lid (boil for 10 minutes).
• 🥄 Plastic food containers (only new ones, with a tight lid).

Not suitable: matchboxes, bags, foil, containers food (even washed).

Does diet affect the results of stool analysis?

Absolutely! 3-5 days before collection, exclude:

• 🍖 Meat and offal —they distort the test for occult blood.
• 🥕 Beets, blueberries, pomegranates —they color feces.
• 🥛 Dairy products —affect pH and microflora.
• 💊 Iron, bismuth, activated carbon —change color and consistency.

For analysis on carbohydrates (for children) fruit juices and sweets should not be given 12 hours before collection.