Collecting biological material for laboratory research often becomes a task that requires precise timing. Many patients are faced with a dilemma: can a sample be collected in the evening in order to give it in the morning, or will this spoil the result? Sample freshness is a critical factor affecting the reliability of the diagnosis of various diseases of the gastrointestinal tract.
Under ideal conditions, laboratory technicians prefer to receive material collected no more than 2 hours ago. However, the realities of modern life, laboratory work schedules and human physiological characteristics, especially when it comes to children, dictate their own rules. Refrigerator compartment becomes the only available way to preserve the properties of feces for a short period. Proper storage allows you to slow down the processes of fermentation and bacterial growth, which will inevitably begin at room temperature.
In this article we will analyze in detail the permissible time intervals for different types of research, packaging rules and temperature conditions. Violation of these standards may lead to false positive or false negative results, which will require repeated testing and loss of time. Understanding the biochemical processes occurring in the sample outside the body will help you properly prepare for your visit to the clinic.
⚠️ Attention: If you are taking antibiotics or bismuth preparations, inform your doctor about this, as they can affect the color and composition of the sample, regardless of storage time.
General principles for the safety of biomaterial
The main task when collecting feces is to minimize contact with the external environment and prevent changes in the chemical composition. Immediately after defecation, microorganisms begin to actively multiply in the mass, and enzymes continue to break down nutrients. Temperature conditions is the main lever for controlling these processes. Cooling slows down the metabolism of bacteria, but does not stop it completely.
Only the main chamber of the refrigerator is suitable for storage, where the temperature is kept in the range from +2 to +6 degrees Celsius. The door is absolutely not suitable for these purposes due to constant temperature changes when opening. Also, you should not place the container near the freezer, where there is a risk of partial freezing, which will destroy the cellular structure of the sample.
It is important to use sterile containers, which are sold in pharmacies. Such containers are sealed and do not react with biological fluids. Glass jars It is not recommended to use baby food or food containers, as residual detergents or fats can distort the chemical analysis. If there is no special container, you can use a glass container with a screw-on lid, after boiling it and drying it.
Dependence of timing on the type of study
Not all tests are equally demanding in terms of delivery time. Different testing techniques detect different pathogens or changes, and the rate of degradation of these markers varies significantly. Therefore, there is no universal answer to the question “how long can you store” - it all depends on the doctor’s prescription.
The most sensitive analysis is for occult blood i bacteriological culture. In these cases, time is against the patient. For scatology (general analysis), the requirements are slightly less stringent, but strict restrictions apply here too. Below is a table systematizing the permissible storage periods depending on the purpose of the study.
| Type of analysis | Maximum period at +4°C | Optimal period | Risk of error |
|---|---|---|---|
| Bacterial culture (dysbacteriosis) | Not recommended | Up to 2 hours | High (death of flora) |
| Eggs of worms and protozoa | Up to 8-10 hours | Up to 4 hours | Medium (destruction of membranes) |
| Occult blood | Up to 6 hours | Up to 3 hours | High (hemoglobin oxidation) |
| Coprogram (general) | Up to 8 hours | Up to 4 hours | Low/Medium |
Particular attention should be paid to analysis for dysbacteriosis. Live cultures of bacteria that inhabit the intestines are extremely sensitive to oxygen and temperature changes. Even short-term refrigeration can change the ratio of aerobic to anaerobic microorganisms, leading to misdiagnosis. In such cases, it is better to collect the material immediately before going to the laboratory, even if you have to get up in the middle of the night.
Storage rules for adult patients
An adult is able to control the process of defecation, which simplifies the task of collecting material. However, there are nuances here too. If you plan to store the sample, you will need to prepare a place in the refrigerator in advance. The container should stand on a shelf, not on the door, and be protected from accidental fall or contamination by other products.
When collecting, it is important to avoid contact with urine. To do this, you can use a clean bedpan or stretch plastic wrap over the toilet (if it is clean and disinfected), but it is better to use special tools. After collection, the material is tightly closed with a lid. The tightness of the packaging prevents the sample from drying out and the spread of odors.
If more than 8 hours have passed before delivery to the laboratory, even if all storage conditions are met, the result may be uninformative. Enzymes continue to work, the pH of the environment changes. In the morning, immediately after waking up, you need to remove the container and transport it in a thermal bag or simply in a bag, avoiding direct sunlight.
⚠️ Attention: Do not freeze feces in the freezer! Ice crystals destroy the epithelial cells and shells of helminth eggs, making the analysis useless.
Nuances of collection and storage in children
With young children the situation is more complicated, since it is impossible to predict the moment of defecation. Parents often wonder whether it is possible to collect stool in the evening if the child only goes to the toilet at night. For tests for eggs, worms and protozoa, storage in the refrigerator until the morning (about 6-8 hours) is allowed and is often the only possible option.
For collection from infants who wear diapers, do not squeeze the material out of the diaper. The absorbent granule instantly absorbs the liquid fraction, leaving only dense particles, which distorts the picture. It is necessary to use a special urinal bag (sterile bag with Velcro) or place a clean diaper/oilcloth under the bottom at the time of bowel movement.
If the child is older and potty trained, the potty should be thoroughly washed with soap and scalded with boiling water. The use of chemical disinfectants (bleach, Domestos) is prohibited, as their vapors can settle on the walls and kill bacteria in the sample. After collection, the material is immediately transferred to a sterile container and stored in the cold.
What to do if a child pooped in a diaper with gel?
It is impossible to collect analysis from such a diaper. The gel turns to jelly and mixes with the stool, rendering the sample unusable. Use a sterile diaper or trap bag secured inside a clean diaper (without gel).
Technical aspects: packaging and temperature
Correct packaging is 50% of the success of the analysis. The container should be about one-third full. Too much material can lead to a violation of the seal during transportation, and too little will not allow the laboratory technician to carry out all the necessary manipulations. Different types of analyzes have their own volume requirements, but a standard pharmacy container is usually sufficient.
The temperature in the refrigerator must be stable. Sudden changes, such as opening the door frequently or placing hot food inside, can cause condensation inside the container. Moisture inside the sample is a risk factor for the proliferation of foreign microflora. Condensation can also lead to lysis (destruction) of cells, which is especially important for coprograms.
When transporting in the winter, the sample should not be allowed to freeze, and in the summer - overheating. It is best to use a small cooler bag containing coolant, but do not place the sample in direct contact with ice. The travel time to the laboratory should not exceed 1-2 hours if you take the material with you after removing it from the refrigerator.
☑️ Check before going to the laboratory
Risks of long-term storage and errors
Why can’t you store feces for days? In addition to the proliferation of bacteria, a change in physicochemical properties occurs. Color, smell, consistency changes. But the most important thing is that the microscopic picture changes. Leukocytes are destroyed, red blood cells are oxidized. If the doctor is looking for inflammation (white blood cells), and you kept the sample for 12 hours, the result will be false negative.
Long-term storage also affects the detection of parasites. The eggs of some helminths can float or, conversely, sink to the bottom, changing the distribution in the mass. Protozoa, such as Giardia, in cold conditions turn into a cyst form or are destroyed, which makes them invisible to the microscope. False diagnosis can lead to treatment not being prescribed on time.
Storing in an unsterile container is also an error from under food. Residues of fat, spices or detergent may react with the reagents in the laboratory. For example, fat can be mistaken for undigested food (steatorrhea), which will lead to a diagnosis of “pancreatitis” in a healthy person.
⚠️ Attention: If you notice that foam has formed in the container, the color has changed to an unnatural one, or a strong unpleasant odor has appeared that is different from usual, such material cannot be donated.
Frequently asked questions (FAQ)
Is it possible to donate feces that have been in the refrigerator all night (10-12 hours)?
To test for eggs of worms and protozoa - as a last resort, you can, but the information content is reduced. For bacterial culture, occult blood and coprogram, such material is no longer suitable, since biochemical processes will significantly change the composition. It is better to collect a new sample.
Does the fact that the stool was frozen and then thawed affect the analysis?
Yes, the influence is critical. Freezing destroys cellular structures, helminth eggs and bacteria. Such a sample is considered defective and cannot be examined. The result will be false in 100% of cases.
Is it necessary to warm up stool from the refrigerator before donating?
No, you cannot warm up the sample. This will trigger the active proliferation of bacteria. The material must be delivered to the laboratory in the form in which it was stored (refrigerated), but not frozen. The laboratory itself will bring it to the required temperature for microscopy.
Is it possible to store feces in the refrigerator door?
It is strictly not recommended. The door is the warmest place in the refrigerator with constant temperature changes when opening. This does not provide stable cooling and can lead to deterioration of the biomaterial faster than on the shelf.
How many hours before the test should you not take a laxative?
Usually laxatives, enemas and rectal suppositories are canceled 2-3 days before the test so that the intestines restore their natural motility and microflora. However, the exact timing depends on the type of analysis, so consult your doctor.