Collecting biomaterial for laboratory research often raises questions among patients, especially when it comes to morning tests. Many people do not have time to deliver the container to the clinic immediately after defecation, which raises doubts about the reliability of the results. Doctors often hear the question of whether it is permissible to leave a sample in the cold and how long it retains its diagnostic properties.
Proper storage of biomaterial is a critical step on which the accuracy of the diagnosis depends. Violation of the temperature regime or time frame can lead to the proliferation of foreign bacteria or the death of pathogenic microorganisms, which will distort the picture of the disease. In this article, we will analyze in detail the permissible periods and conditions for keeping samples until they are transferred to the laboratory.
Important to understandthat there is no universal answer for all types of analyzes. Different research methods require different conditions for preserving biological samples. What is acceptable for a coprogram may be categorically unacceptable for identifying hidden blood or parasites.
⚠️ Attention: These recommendations are for reference only. Always check the current requirements in the laboratory where you plan to take the test, since the reagents used there may require special transportation conditions.
Dependence of the timing on the type of study
The first thing you need to do before collecting the material is to find out what kind of analysis the doctor prescribed. The type of study directly determines how long the biomaterial remains suitable for diagnosis. Coprogram is considered the most stable test, while the search for the simplest organisms requires maximum efficiency.
If you are scheduled for a study on occult bloodthen the quality of preparation and storage is subject to increased requirements requirements. At room temperature, enzymes contained in feces begin to actively destroy hemoglobin, which can lead to a false negative result. In such cases, a delay of even a few hours can be critical.
- 🔬 Coprogram is the most stable analysis, allowing storage for up to 8-12 hours.
- 🦠 Bacteriological culture - requires delivery within 2-3 hours, sometimes up to 6 hours are allowed in special environments.
- 🩸 Analysis for hidden blood - optimally 3-4 hours, maximum up to 6 hours in the cold.
- 🪱 Search for eggs of worms and protozoa - strictly up to 2-4 hours, since the larvae quickly die or change morphology.
For most standard procedures The maximum permissible storage period in a household refrigerator is 8 hours., however, delivery within the first 2-3 hours after bowel movement remains the gold standard. Prolonged exposure of a sample to low temperature conditions slows down, but does not completely stop, biochemical processes.
Optimal temperature conditions
Temperature plays a decisive role in the safety of the biomaterial. The main mistake patients make is placing the container in the freezer or on a shelf near the wall of the refrigerator, where the temperature can drop below zero. Freezing the sample is strictly prohibited, as ice crystals destroy cellular structures.
The ideal place to temporarily place the container is the middle shelf of the refrigerator. It is there that the most stable temperature is maintained, usually ranging from +2 to +6 degrees Celsius. The refrigerator door is not suitable for these purposes due to constant temperature changes when opening.
It is necessary to ensure the tightness of the container to prevent contact of the contents with food and other surfaces. Sterility The external surface of the jar is also important to prevent the entry of foreign microorganisms from the outside, although for the internal environment this is less critical if the lid is closed tightly.
Requirements for collection container
The quality of the container directly affects the safety of the sample. To collect stool, you must use only special sterile containers, which are sold in pharmacies. They are made of chemically inert plastic that does not react with the components of the biomaterial.
The use of glass jars for baby food or mayonnaise, even thoroughly washed, is not recommended. Microscopic particles of detergent or organic residues may remain on the walls of such dishes, which can distort the chemical composition of the sample during biochemical analysis biochemical analysis.
Many pharmaceutical containers come with a special spoon built into the lid. It allows you to take material from different parts of feces, which increases the information content of the study. The volume of collected material should be approximately the size of a walnut or 5-10 grams.
☑️ Checking readiness for collection
Rules for collecting biomaterial
The collection process must take place under conditions that prevent urine, toilet water or menstrual blood from entering the sample. To do this, you can use a clean plastic bag stretched over the toilet seat, or a special vessel pre-treated with boiling water.
It is best to collect the material in the morning, immediately after waking up. If defecation occurred in the evening, then storage in the refrigerator is allowed only for coprogram and occult blood analysis, and then with time restrictions. Evening collection to search for parasites is practically not informative.
After placing the material in the container, it must be tightly closed and immediately placed in a cool place. Do not keep the jar at room temperature for more than 15-20 minutes before putting it in the refrigerator. Rapid cooling helps stop the growth of bacteria.
| Type of analysis | Max. time at +2...+6°C | Is it possible to freeze | Optimal delivery time |
|---|---|---|---|
| Coprogram | up to 12 hours | No | up to 8 hours |
| Occult blood | up to 6 hours | No | up to 4 hours |
| Eggs of worms | up to 4 hours | No | up to 2 hours |
| Bacterial culture | up to 3 hours | No | up to 2 hours |
Frequent errors during storage
One of the most common mistakes is an attempt to extend the shelf life of a sample by placing it in the freezer. Freezing completely destroys the structure of cells and microorganisms, making the analysis meaningless. After defrosting, the biomaterial turns into a heterogeneous mass, unsuitable for microscopy.
Another mistake is storing the container unsealed. If the lid is not closed tightly, the stool may become airy, changing its consistency and chemical composition. In addition, it violates sanitary standards and can lead to contamination of other products in the refrigerator.
⚠️ Attention: Never add water, preservatives or other liquids to the container unless specifically indicated in the instructions for the specific test system (for example, some home testing kits may contain preservative solutions).
Some patients try to preserve the material by placing it on balcony in winter. This cannot be done because the temperature there is not controlled and can be too low (freezing) or too high (daytime sun). The refrigerator is the only safe place at home.
What to do if there was no bowel movement in the morning?
If the test needs to be taken urgently, but bowel movement did not occur in the morning, you can try to induce it naturally (light abdominal massage, a glass of warm water). It is prohibited to use laxatives or enemas before collecting coprograms and searching for worm eggs, as this will distort the results. In this case, it is better to postpone the test to the next day.
Storage specifics for children and infants
Collecting tests in young children is often difficult due to the unpredictability of the defecation process. For infants, it is convenient to use urinals, but only special ones designed for feces, or clean plastic film secured under the bottom.
The absorbent surfaces of diapers cannot be used. Gel absorbents instantly absorb the liquid fraction, leaving only dense particles on the surface, which makes the analysis uninformative. Also, you should not squeeze the contents of the diaper into the container.
The shelf life of children's biomaterial is the same as for adults, but the requirements for efficiency are often higher due to the smaller volume of the sample. Microflora The child's intestines are very sensitive, and any changes begin quickly. Try to deliver the container to the laboratory as soon as possible.
When the analysis is considered spoiled
It is not always possible to visually understand that the biomaterial has deteriorated, but there are a number of signs indicating the unsuitability of the sample. If you notice a change in color, the appearance of mold or a sharp change in odor (different from usual), such material cannot be used.
Also a sign of deterioration is the separation of the contents of the container, the appearance of foam or gas formation, if transparent. However, even in the absence of visible changes, exceeding the temporary storage limits makes the result unreliable.
The laboratory technician, under microscopy, will immediately see signs of cell decay or proliferation of saprophytic flora, which normally should not dominate. In this case, they will simply refuse to conduct the study or give you a result with a note that the material is unsuitable, and the money for the analysis may not be returned.
Is it possible to store feces in the refrigerator for more than 12 hours?
It is strictly not recommended. After 12 hours, even at low temperatures, irreversible decomposition processes begin. The results of such an analysis will be false, which can lead to incorrect treatment or its absence.
Does tightly closing the lid affect the result?
Yes, it does. A loose lid leads to drying out of the sample and oxidation of its components by atmospheric oxygen. This changes the pH environment and can destroy some types of bacteria important for diagnosis.
What to do if the container is dropped and the outside is dirty?
If the outside of the container is dirty, wipe it with a disinfectant solution (for example, an alcohol wipe), being careful not to touch the lid and not break the seal. If there is a risk of dirt getting inside through a loose lid, it is better to dispose of the material.
Does it need to be heated before handing over the container?
No, you cannot heat the sample. A sudden change in temperature can cause bacteria to multiply. Deliver the material in the form in which it was stored (in a bag or cooler bag) to minimize heating along the way.
Is it possible to get tested if you have taken charcoal?
Activated carbon and other sorbents, as well as bismuth and iron preparations can color stool and make diagnosis difficult. You should inform your doctor and laboratory technician about their use. It is usually recommended to wait 2-3 days after stopping the medications.