Collecting biomaterial for laboratory research is a procedure that requires strict adherence to hygiene rules and temperature conditions. Often patients are faced with a situation where it is not possible to deliver the container to the laboratory immediately after a bowel movement, for example, if the test is scheduled for early morning and the clinic is open from 8:00. In such cases, a natural question arises about how long the biological material retains its properties when cooled. Coprogram is one of the most informative studies, but it is also the most demanding on the freshness of the sample.
Improper storage can lead to distorted results, since feces continue to biochemical processes even after leaving the body. Enzymes, bacteria and epithelial cells under the influence of temperature begin to quickly change their structure or collapse. Therefore, understanding time frame and the conditions of the container is critical for obtaining a reliable diagnosis and prescribing the correct treatment.
In this article we will analyze in detail the permissible storage time of feces in a household refrigerator, the influence of temperature on various types of tests and typical mistakes that patients make when collecting material. Compliance with these recommendations will help to avoid the need to re-take the analysis and waste of time.
Optimal conditions for preserving biomaterial
The main factor affecting the safety of the sample is temperature. To slow down the growth of bacteria and stop enzymatic processes, the container must be placed in the cold. However, not all refrigerator compartments are suitable for this purpose. The optimal zone is considered to be the middle shelf or door, where the temperature ranges from +2 to +6 degrees Celsius.
It is important to understand that freezing biomaterial is strictly prohibited. Ice crystals formed during freezing destroy cellular structures, which makes microscopic examination impossible. Low temperature should only preserve the state of the sample, but not change its physical form. If you notice that the material has frozen, it should be disposed of and a new one collected.
⚠️ Attention: Do not store the test container near food, especially open dishes. This violates sanitary standards and can lead to cross-contamination or odor changes, which is important for organoleptic evaluation.
The container must be tightly closed with a lid immediately after collection. This prevents the sample from drying out and introducing foreign microorganisms from the refrigerator air. The tightness also protects against the spread of a specific odor that can be absorbed into other products.
Storage periods for various types of tests
The time during which feces remain suitable for research directly depends on the purpose of laboratory diagnostics. Different tests require the identification of different components: from oocytes to occult blood. Each of them has its own freshness standards.
The simplest coprogram is the most time-sensitive. It evaluates physicochemical properties, the presence of leukocytes, red blood cells and food digestibility. The longer the material sits, the more active the decay processes are in it, changing the pH environment and cell morphology.
- 🕒 Coprogram: ideal period is up to 2 hours, the maximum allowed in the refrigerator is 8-10 hours.
- 🦠 Bacteriological culture: requires delivery within 2 hours, storage is not recommended, as the composition changes microflora.
- 🩸 Analysis for occult blood: allows storage for up to 12 hours, provided preservatives are used in the container.
- 🪱 Eggs of worms: the most stable, the material can be stored in the refrigerator for up to 24 hours without significant loss informative.
It is worth noting that in order to detect Giardia and some types of protozoa, the material must be delivered to the laboratory while still warm, within 15-30 minutes. Cooling in this case can lead to the fact that the mobile forms of protozoa become motionless and will be missed by the laboratory assistant.
Storage specifics for a coprogram
A coprogram is a complex study, therefore the requirements for it are the most stringent. If you cannot deliver the material immediately, short-term storage is allowed. However, it should be remembered that after 3-4 hours, irreversible changes in the composition of fatty acids and salts may begin in the sample.
For maximum safety, it is recommended to use special containers with preservative liquid, if the laboratory provides such an opportunity. Such systems allow you to increase the shelf life of the material to 24-48 hours, since the reagent fixes cells and stops bacterial proliferation.
If you are using a regular sterile container, try to minimize the time the stool is at room temperature before placing it in the refrigerator. The faster you cool the sample, the more accurate the result will be. data-i="82">Shape and color microscopy.
| Parameter | Without refrigerator | In the refrigerator (+4°C) | With preservative |
|---|---|---|---|
| Shape and color | Change after 2 hours | Save up to 10 hours | Save up to 48 hours |
| Leukocytes | Destroyed in 1 h | Stable up to 6-8 hours | Stable up to 24 hours |
| Occult blood | Reaction weakens | Stable up to 12 hours | Stable up to 3 days |
| Helminth eggs | Stable | Stable up to 24 hours | Stable up to 10 days |
Please note Please note that the table is provided for guidance only and your laboratory's specific requirements may vary. Always check the rules for receiving biomaterial at the reception of a medical institution.
Rules for collecting material for an accurate result
The quality of the analysis depends not only on the speed of delivery, but also on the correctness of collection. Feces should be obtained naturally, without the use of enemas and laxative suppositories, which can wash away the microflora or add foreign impurities. Defecation should occur in a clean, dry container (vessel or pot), pre-treated with boiling water.
Small portions are selected for analysis from different parts of the feces: from above, from the side and from the inside. This is especially important if there is mucus, pus or streaks of blood in the stool - they must be included in the sample. The total volume of material should approximately correspond to the size of a walnut or one teaspoon.
☑️ Rules for collecting stool
It is strictly forbidden to allow urine or water from the toilet to get into the container. Urine can contain bacteria that distort the picture of microflora, and toilet water often contains disinfectants that destroy cellular structures. If defecation occurs in water, the test will have to be retaken.
After collection, the container should be immediately tightly closed and placed in a cool place. If you live far from the laboratory, use a thermal container or cooler bag for transportation to maintain a stable temperature along the way.
Typical mistakes during transportation and storage
One of the most common mistakes is storing the container on the refrigerator door. When the door is opened frequently, the temperature in this compartment fluctuates, creating unfavorable conditions for the sample. In addition, there is a risk of accidentally knocking over or damaging the packaging.
Another mistake is using unsterile containers. Even a thoroughly washed mayonnaise jar may contain microparticles of fat or detergent. These substances react chemically with reagents in the laboratory, resulting in false positive or false negative results.
⚠️ Attention: Do not try to “refresh” an old analysis by stirring it or adding water. This is guaranteed to ruin the sample. If more than 12 hours have passed since defecation (without a preservative), the material is considered unsuitable.Some patients mistakenly believe that the colder the better, and put the container in the freezer. As mentioned, this destroys the structure of the cells. Also, you should not place the container directly at the back wall of the refrigerator, where the temperature can drop below zero.
What to do if you haven’t had a bowel movement for several days?
If you have taken a laxative or given an enema to induce a bowel movement, you should definitely notify your doctor about this. For some tests (for example, for occult blood or microflora), such material will not be suitable, and the study will have to be postponed until natural bowel movement.
How to properly deliver the analysis to the laboratory
Transportation is the final stage, on which a lot also depends. In summer or when traveling on public transport for a long time, use refrigerants. It is better to wrap the container in a paper towel and place it in an opaque bag to hide the contents and protect it from direct sunlight.
Upon arriving at the laboratory, do not give the container away immediately. Make sure it has a sticker with your details and the date and time of collection. If you store the material at home for more than 6 hours, indicate the exact time of defecation on the referral, this will help the laboratory assistant make adjustments for possible changes.
Remember that compliance with storage rules is primarily your interest. Repeated collection of material due to a damaged sample is an extra waste of time, money and emotional stress.
Is it possible to donate feces collected in the evening of the previous day?
For coprogram and analysis for worm eggs, this is allowed provided it is stored in the refrigerator at a temperature of +2...+6°C for no more than 8-10 hours. Evening material is not suitable for bacteriological sowing and searching for protozoa.
Does the fact that the container has been left at room temperature for 1 hour affect the analysis?
A short-term stay at room temperature (up to 1 hour) before placing in the refrigerator or delivery is, as a rule, not critical for most indicators, except for the search for living forms of protozoa. However, it is better to minimize this time.
Is it necessary to heat the container before handing it in if it was in the refrigerator?
No, you cannot heat the material. A sudden change in temperature can trigger condensation processes inside the container and affect the consistency. The laboratory is conducting research taking into account the fact that the material could have been in the cold.
What to do if foreign objects are found in the stool?
If you notice threads, hair or particles of undigested food (except plant fibers) in the container, this should be noted. But the material itself will most likely be accepted if it is collected in a sterile container.