Taking tests is stressful for the body, and proper preparation for laboratory tests often becomes a real test for the patient. Especially many questions arise around the collection of biomaterial for scatology, when it is necessary to know exactly how long the collected sample retains its diagnostic properties. Improper storage can lead to distorted results, which in turn threatens incorrect diagnosis and ineffective treatment.
Time is the most critical factor when working with biological samples. Biochemical processes in feces do not stop after defecation, but continue to occur at different speeds depending on the ambient temperature. Understanding how much stool can be stored in the refrigeratoris key to maintaining the reliability of data on the state of the gastrointestinal tract.
In this article we will analyze in detail the temperature conditions, acceptable time intervals and typical mistakes that patients make when collecting material. You will learn how to properly use preservatives, why the freezer is a taboo, and what nuances exist for different types of laboratory research.
Biochemical processes and the effect of time on a sample
After the biomaterial has left the body, irreversible changes begin in it. Enzymes contained in stool continue to break down proteins, fats and carbohydrates, which changes the chemical composition of the sample. If you are planning to donate coprogram, it is important to consider that after just a few hours the pH of the environment may shift, and the number of leukocytes and red blood cells may change due to their destruction.
Temperature plays a decisive role in slowing down these processes. At room temperature, bacteria multiply exponentially, which can lead to false-positive results for occult blood or pathogenic flora. That is why the question of how much stool is stored under different conditions comes to the fore when preparing for analysis.
Cooling allows you to “preserve” the state of the sample, significantly reducing the activity of enzymes and the rate of division of microorganisms. However, even low temperatures do not stop the processes completely, but only slow them down. Therefore, there is a strictly regulated time period during which delivery of the material to the laboratory is considered acceptable.
⚠️ Attention: Long-term storage, even in the cold, leads to crystallization of salts and changes in the structure of the fibers, which makes microscopic examination impossible. Do not try to store the sample longer than the recommended time.
Optimal storage periods depending on the type of analysis
The answer to the question of how long you can keep the material in the cold directly depends on what kind of research will be carried out. Laboratories have different requirements for sample freshness for coprogram, eggworm test, or bacterial culture. There is no universal rule “for all cases”, and ignoring these differences can lead to sample rejection.
For a standard coprogram, which includes macroscopic, microscopic and chemical examination, the deadlines are the most flexible, but still limited. If it is necessary to identify the eggs of worms or protozoa, the time window narrows, since some types of parasites quickly change their morphology or are destroyed. Bacteriological inoculation requires maximum sterility and freshness so that the opportunistic intestinal flora does not have time to suppress the growth of the desired pathogens.
Below is a table systematizing the permissible storage time for various types of research, subject to compliance with the temperature regime:
| Type of research | Maximum time at +4...+8°C | Requirements for containers | Admissibility of freezing |
|---|---|---|---|
| Coprogram (general analysis) | up to 8-10 hours | Sterile container | Strictly prohibited |
| Eggworm analysis | up to 5-6 hours | Clean dry container | Not recommended |
| Occult blood | up to 6 hours | Special container | Prohibited |
| Bacterial culture | up to 2-3 hours | Sterile container with preservative | Prohibited |
It is important to understand that the specified time frames are only relevant if collected correctly. If the biomaterial has been in contact with water, urine or disinfectants, its diagnostic value drops to zero regardless of storage time. Sterility and isolation from the external environment are basic requirements for any type of analysis.
Rules for collecting and preparing the container
The quality of the result begins not in the laboratory, but at the moment of collecting the biomaterial. For scatology, collecting from the surface of the toilet bowl is absolutely not suitable, since there may remain traces of detergents, bleach or water, which destroy cellular elements and change the chemical composition. Use only special sterile containers that are sold in pharmacies and are inexpensive.
If using a special container is not possible, you can use a clean glass jar with a tight-fitting lid. However, such containers must first be sterilized with boiling water and thoroughly dried. It is not recommended to use plastic containers from food products, as residual fats or spices may react with reagents.
The collection process should proceed as follows:
- 🧼 Prepare a clean surface in advance (pot, vessel or cling film stretched over the toilet), excluding contact with water.
- 💩 Take the material with a special spoon built into the lid of the container from 3-4 different places of the fecal mass.
- 🔒 Close the container tightly to prevent air from entering and drying out the sample, which also affects the result.
- 🏷️ Immediately label the container, indicating Full name and time of collection, so as not to confuse samples if there are several of them.
The volume of material is also important. For most studies, a volume equal to one or two teaspoons is sufficient. Too much feces in the container can lead to uneven cooling and faster start of rotting processes in the center of the sample.
☑️ Correct collection of material
Temperature conditions and conditions in the refrigerator
Where exactly in the refrigerator is it best to store a container with biomaterial? Many patients make the mistake of leaving the jar on the door or against the back wall, where the temperature may fluctuate or be too low. The optimal place is the middle shelf, away from the freezer and heat sources.
The temperature should strictly correspond to the range from +2 to +8 degrees Celsius. At higher temperatures, bacteria continue to actively multiply, and at lower temperatures (closer to 0), the crystallization process can begin, which will destroy the structure of epithelial cells and leukocytes. Thermal stability is the key word for successful storage.
The container should not be placed next to the products food, especially with meat, fish or prepared foods, to eliminate the risk of cross-contamination and introduction of foreign odors, although this is more a matter of hygiene than impact on the analysis. It is also important to avoid direct contact of plastic with the ice crust on the walls of the refrigerator.
⚠️ Attention: Never freeze feces! Freezing leads to rupture of cell membranes and complete loss of the diagnostic value of the sample. If the material is frozen, it must be disposed of and a new one collected.
Errors that make the analysis useless
Even if you know exactly how many hours you can store stool, there are other factors that can spoil the sample. One of the most common mistakes is collecting material after an enema or taking X-ray contrast agents. In such cases, the sample will contain foreign inclusions, which the laboratory technician may mistake for pathology.
Taking medications also distorts the picture. Antibiotics, bismuth, iron and barium preparations change the color, consistency and chemical composition of feces. If discontinuation of the drug is impossible for health reasons, you must warn the doctor and laboratory assistant about this, but it is better to pause before taking the test.
Another common mistake is using unsealed containers. If the lid is not closed tightly, the sample dries out and develops artifacts that interfere with microscopy. In addition, an open container is a risk of spreading infection and an unpleasant odor in the refrigerator where food is stored.
Is it possible to collect stool in the evening?
Yes, if the analysis is scheduled for the morning hours of the next day. Evening collection is acceptable for coprograms and searching for helminth eggs, but is absolutely not suitable for analysis for dysbacteriosis and occult blood, where maximum freshness is important. The evening sample should be stored strictly in the refrigerator at +4°C for no more than 8-10 hours.
Storage specifics for children and infants
Collecting tests from young children is a separate category of tasks that requires special skill. A potty should not be used for infants, as it is rarely perfectly clean, and remnants of detergents or previous feces can contaminate the sample. The ideal option is to use a sterile urine bag, which is glued to the skin around the anus.
If a child goes to the potty, it must be thoroughly washed with soap, rinsed with boiling water and dried before use. It is impossible to collect feces from a diaper or diaper, since the absorbent instantly absorbs the liquid fraction, leaving only dense particles, which violates the ratio of elements in the sample.
The storage time of children's biomaterial is the same as for adults, but the requirements for delivery speed are often higher due to the smaller volume of the sample, which cools faster or, conversely, heats up. Try to deliver the container to the laboratory within 2-3 hours after defecation, even if more time is formally allowed.
When storage is not possible: alternative solutions
There are situations when it is impossible to comply with storage conditions: for example, the refrigerator is broken, or you are on a trip. In such cases, the only right decision is to collect the material immediately before going to the laboratory or use the services of on-site collection of tests, which are provided by many private clinics.
If the test is scheduled for early in the morning, and the child or adult cannot empty the intestines at the right time, do not try to stimulate the process with enemas or laxatives without the consent of the doctor. It is better to postpone the test to the next day than to get a false result and start unnecessary treatment.
In emergency cases, when minutes count (for example, if an acute intestinal infection is suspected in a hospital), the material is delivered to the laboratory in a thermostat or a special shipping container immediately after defecation, without the home storage stage.
Frequently asked questions (FAQ)
Is it possible to store feces for scatology in the freezer if you need to keep it longer?
No, you absolutely cannot freeze feces for scatology. Ice crystals destroy cellular structures, white blood cells and red blood cells, making microscopic examination impossible. Some chemical compounds are also destroyed. The frozen sample will have to be retaken.
What to do if the feces have been in the refrigerator for 12 hours?
Most likely, such a sample is no longer suitable for qualitative analysis. Within 12 hours, even at low temperatures, significant changes occur in the composition of the microflora and the structure of the fibers. The result may be false. It is better to collect new material so as not to treat non-existent diseases.
Is it necessary to add preservatives to feces for storage?
For a standard coprogram, preservatives are not needed and are even harmful. They are used only in special containers for specific types of tests (for example, for occult blood or types of parasites), which are issued by the laboratory as prescribed by a doctor. You don’t need to add anything to a regular jar.
Is it possible to donate feces if it was collected in the evening of the previous day?
Yes, for coprograms and searching for worm eggs, evening collection is acceptable, provided it is stored in the refrigerator at a temperature of +4...+8°C for no more than 8-10 hours. This option is not suitable for analysis for dysbacteriosis or hidden blood - only fresh morning material.