Stool analysis is one of the most common laboratory tests, which is prescribed for the diagnosis of gastrointestinal diseases, parasitic infections, dysbacteriosis and other pathologies. However accuracy of results directly depends not only on the correct collection of the material, but also on its storage before delivery to the laboratory. Many patients are faced with the question: is it possible to store feces in the refrigerator, and if so, for how long?
Doctors and laboratory technicians are unanimous: the ideal option is to deliver the material to the laboratory within 1-2 hours after collection. But life makes adjustments: clinic schedules, distance from home, morning traffic jams or sudden circumstances may force you to postpone your visit. In such cases, the refrigerator becomes temporary storage. However, it is important to follow strict rules here, otherwise the analysis will have to be retaken.
In this article we will figure out how long you can store stool in the refrigerator for different types of studies, what temperature is optimal, what containers are suitable, and what mistakes most often lead to distorted results. Let us separately dwell on the nuances for children, pregnant women and patients with chronic diseases.
Why it is important to observe the storage periods of feces
Feces are biological material that begins to decompose immediately after defecation. It contains bacteria, enzymes, epithelial cells, food debris and, in the presence of pathologies, parasites or their eggs. At room temperature, these components interact with each other, which leads to:
- 🔬 Bacterial proliferation —some microorganisms (for example, Escherichia coli) actively divide, distorting the real picture of the microflora.
- 🧬 DNA breakdown of parasites —helminth eggs or protozoan cysts may be destroyed, and the analysis will show false negative result.
- 📉 Changes in the chemical composition —enzymes break down fats, proteins and carbohydrates, which affects the coprogram.
The refrigerator slows down these processes, but does not stop them completely. For example, at a temperature of +4°C, the growth of most bacteria stops, but some species (for example Clostridium) can survive and reproduce. Therefore even in the refrigerator, the shelf life of stool is limited..
Critical moment: if the test is taken for occult blood (Gregersen reaction), hemoglobin in the stool begins to oxidize after 6-8 hours, and the test can give a false negative result. For such a study, storage in the refrigerator is permissible only as a last resort!
Permissible periods for storing stool in the refrigerator for different tests
Storage periods depend on the type of study. Below is a table with recommendations for the most common analyses:
| Type of analysis | Maximum shelf life in the refrigerator (+4°C) | Notes |
|---|---|---|
| Coprogram (general analysis) | 8–12 hours | It is advisable to deliver within 4–6 hours. Long-term storage distorts data on mucus, leukocytes and muscle fibers. |
| Analysis for helminth eggs (helminths) | up to 24 hours | Ascaris and pinworm eggs last longer, but Giardia cysts can collapse after 12 hours. |
| Analysis for dysbacteriosis | 4–6 hours | Bacteria die or multiply, distorting the microflora ratio. Some laboratories require delivery within 2 hours. |
| Occult blood test | 6–8 hours | Hemoglobin is oxidized, a false negative result is possible. Some clinics do not accept material after 4 hours of storage. |
| Analysis for carbohydrates (for infants) | 4 hours | Lactase and other enzymes quickly break down carbohydrates, the data becomes inaccurate. |
Important: some private laboratories (for example Invitro, Helix) can set their own rules. Check the storage time when you sign up for analysis!
If you are being tested for PCR diagnostics of infections (for example, rotavirus or norovirus), storage in the refrigerator is permissible for no more than 6 hours. Such tests often require a special transport container with a preservative, which is provided by the laboratory.
At what temperature to store stool in the refrigerator
The optimal temperature for short-term storage of stool is +2°C to +8°C. This is the standard mode of a household refrigerator (usually +4°C on the middle shelves). However, there are nuances:
- ❄️ Do not store in the freezer! Freezing destroys parasite cells and changes the structure of bacteria. An exception is special tests for which the laboratory issues freezing instructions.
- 🔥 Do not place it next to foods that generate heat (for example, next to the door or above the compressor). The temperature there can rise to +10°C.
- 🧊 Use the coldest zone —usually the bottom shelf above the vegetable compartment.
⚠️ Attention: If your refrigerator has function No Frost or Super cooling, check if the temperature drops below +2°C. This can lead to partial freezing of the sample and distorted results.
For maximum accuracy, you can use Thermal container with ice (temperature +2°...+4°C). Such containers are sold in pharmacies or medical equipment stores. They are especially useful if you are taking the test to the laboratory in hot weather.
How to properly collect and store feces for analysis
Not only the timing, but also collection method affects the reliability of the results. Follow this algorithm:
For 2-3 days, eliminate coloring foods (beets, blueberries) and alcohol from your diet|
Do not take antibiotics, laxatives or iron supplements (unless agreed with your doctor)|
Buy a sterile container with a spoon at the pharmacy (do not use matchboxes or jars!)|
Wash the perianal area with warm water without soap before defecation|
Collect material from different parts of the stool (at least 1-2 g, the volume of a walnut nut)-->
After collection:
- Close the container tightly with the lid.
- Sign it (full name, date and time of collection).
- Place in the refrigerator on the middle shelf (not in the door!).
⚠️ Attention: If a child, especially an infant, takes the test, collect stool a clean diaper or potty. Do not take material from a diaper - the absorbent gel can get into the sample and distort the results.
For analysis on occult blood 3 days before collection, exclude meat, fish, and green vegetables from your diet vegetables and preparations with iron. Even a small amount of hemoglobin from food can give a false positive result.
What to do if you were unable to collect stool in the morning?
If defecation occurred in the evening, and the laboratory accepts tests only in the morning, collect the material in a sterile container and store in the refrigerator at +4°C. The main thing is to meet the acceptable deadlines for your type of analysis (see table above). If more than 12 hours have passed, it is better to repeat the collection in the morning.
Errors that spoil the stool analysis
Even if you stored the stool correctly in the refrigerator, some errors can make the analysis uninformative. Common mistakes:
- 🚫 Use of non-sterile containers —jars of baby food or mayonnaise contain residual fat and bacteria.
- 🚫 Collecting feces after an enema or candles —this distorts the microflora and chemical composition.
- 🚫 Storage in the freezer - destroys the structure of parasites and cells.
- 🚫 Delivery to the laboratory in hot weather without thermal container - at +25°C and above the material deteriorates in 1-2 hours.
- 🚫 Collecting feces from the toilet —disinfectants and water dilute the sample.
Another common mistake is long-term storage of stool for analysis for dysbacteriosis. Many bacteria (for example, bifidobacteria) die within 4 hours, even in the refrigerator. As a result, the laboratory may not detect their deficiency, although in fact it exists.
If you doubt whether the material was collected correctly, it is better to retake the analysis. For example, if giardiasis is suspected, sometimes it is necessary to test stool 3 times with an interval of several days, since cysts are not constantly excreted.
What to do if more than the permissible storage period has passed
If you did not manage to deliver the stool to the laboratory on time, do not try to “save” the analysis. Here's what you can do:
- 🔄 Retake the test —this is the most reliable option. It is especially critical for tests for hidden blood and dysbacteriosis.
- 📞 Call the laboratory —some clinics allow storage for up to 24 hours for certain tests (for example, for worm eggs).
- ❄️ Use a preservative —for some tests (for example, for rotavirus), the laboratory issues a special solution that extends the shelf life.
⚠️ Attention: If the feces have been stored longer than the permissible period, but have not changed in appearance (the smell of rot has not appeared, the color has not changed), this does not mean that the analysis is valid! Microscopic changes may have already occurred.
In some cases, the laboratory technician may accept the material, but make a note about long-term storage. This means that the results may be unreliable, and the doctor will order a repeat analysis.
Features of fecal storage for children and pregnant women
Fecal analysis in children, especially infants, has its own nuances:
- 👶 For newborns a test for carbohydrates (for lactase deficiency) is often prescribed. In this case, the stool must be delivered to the laboratory maximum after 4 hoursas enzymes quickly break down lactose.
- 🧒 For children under 3 years of age when analyzing for worm eggs, it is recommended to collect stool for 3 consecutive days (from 1 day interval). Each sample can be stored for no longer than 12 hours.
- 🤰 Pregnant women if parasites are suspected, a PCR test may be prescribed. For him, feces are stored for no more than 6 hours at +4°C.
For babies under one year old, it is better to use special children's containers with a small spoon (sold in pharmacies). They are more convenient for collecting small amounts of feces.
If a child takes probiotics or antibiotics, a dysbacteriosis test must be taken no earlier than 2 weeks after completing the course. Otherwise, the results will be distorted.
FAQ: Frequently asked questions about storing stool samples
Can stool be stored in the refrigerator in a regular jar?
No. For analysis you need sterile container from the pharmacy. A regular jar may contain detergent residue or bacteria that will skew the results. The exception is if the jar is new, thoroughly sterilized with boiling water and has a tight lid.
What happens if feces were stored in the refrigerator for longer than the permissible period?
The consequences depend on the type of analysis:
- For coprograms —the indicators of mucus, leukocytes and undigested fibers will change.
- For analysis for dysbacteriosis —the ratio of bacteria will become unreliable.
- For hidden blood test a false negative result is possible.
In most cases, the laboratory will ask you to retake the test.
Is it possible to freeze stool for analysis?
Freezing strongly not recommendedsince:
- Ice destroys the shells of parasite eggs.
- Bacteria die, and analysis for dysbacteriosis becomes uninformative.
- The structure of the cells changes, which distorts the coprogram.
An exception is if the laboratory specifically indicated to freeze the sample (for example, for some virological tests).
How to store feces if the laboratory is far away and the journey takes more than an hour?
In this case:
- Use thermal container with ice (temperature +2°...+4°C).
- Place the container with the analysis in thermal bag or wrap towel.
- If the trip takes more than 2 hours, check with the laboratory whether you can use preservative (for example, glycerin or saline).
Some clinics offer the service of courier delivery analysis - this is the best option for remote regions.
Do you need to wash your butt before collecting stool?
Yes, but without soap and gels! It is enough to rinse the perianal area with warm water. Soap can destroy bacteria or parasites on the surface of the skin, which will distort the results (for example, when analyzing for enterobiasis).