A stool test for dysbacteriosis is one of the most “capricious” laboratory tests. Its results directly depend on how correctly the biomaterial was collected, transported and stored. Even minor errors - for example, violation of the temperature regime or exceeding the permissible storage period - can lead to false indicators of microflora, which will distort the clinical picture and complicate the diagnosis.
The main question that concerns patients: how long can you store feces for dysbacteriosis in the refrigeratorso that the results remain reliable? The answer depends on the type of analysis (qualitative or quantitative), the specific laboratory's recommendations, and even the model of your refrigerator. In this article, we will analyze the official standards, the nuances of storage at different temperatures, as well as typical mistakes that 80% of patients make when preparing for analysis.
Important: if you take the test in a private laboratory (for example, Invitro, Helix, Hemotest), check their internal requirements for storage - they may differ from the general rules. Some clinics accept stool only on the day of collection, others allow storage for up to 24 hours at +4°C.
Official standards: how many hours can you store feces in the refrigerator
According to clinical recommendations Russian Society of Clinical Microbiology (ROKMI), the optimal storage period for stool for analysis of dysbacteriosis is no more than 2-3 hours at room temperature (up to +25°C) or up to 12-24 hours at +4...+8°C (in the refrigerator). However, these figures are conditional and depend on the purpose of the study:
- 🔬 Qualitative analysis (determining the presence/absence of microorganisms): allows storage up to 24 hours at +4°C.
- 📊 Quantitative analysis (counting bacterial colonies): no more than 6–8 hours at +4°C, since some microbes may die or multiply.
- 🧪 Analysis for opportunistic flora (for example, Staphylococcus aureus, Candida albicans): maximum 4-6 hours at +4°C.
Why such a scatter? The fact is that at low temperatures, some bacteria (for example, Escherichia coli or Bifidobacterium) slow down their growth, but do not die, while others (for example, Lactobacillus) may partially lose their viability. This distorts the ratio of microflora in the sample.
| Type of analysis | Max. shelf life at +4°C | Max. period at +20…+25°C | Risk of distortion of results |
|---|---|---|---|
| General analysis (coprogram) | 24 hours | 8 hours | Low |
| Dysbacteriosis (qualitative) | 12–24 hours | 3–4 hours | Average |
| Dysbacteriosis (quantitative) | 6–8 hours | 2 hours | High |
| For pathogenic bacteria (Salmonella, Shigella) | 4–6 hours | 1 hour | Very high |
⚠️ Attention: If the laboratory uses the PCR (polymerase chain reaction) method to analyze dysbacteriosis, the storage period can be increased to 48 hours at +4°C, since the method detects the DNA of microorganisms, and not live cultures. However, this is rare - most clinics require “live” bacteria for inoculation.
How to do it correctly. store stool in the refrigerator: step-by-step instructions
Even if you met the required deadlines, improper storage can make the analysis useless. Follow this algorithm:
- Collect the feces in a sterile container. Use pharmaceutical containers with a spoon (for example, "EcoLab" or "MedPlast"). jars of baby food or mayonnaise - there may be fats or detergents on their walls that inhibit bacteria.
- Close the lid tightly. Contact with oxygen accelerates the death of anaerobic bacteria (for example, Bacteroides).
- Place the container in the middle of the refrigerator. The optimal zone is the shelf above the vegetable drawer, where the temperature is stable at +4...+5°C. The refrigerator door is not suitable due to temperature changes when opening.
- Do not freeze! At temperatures below 0°C, bacterial cells are destroyed and the analysis will become uninformative.
Collect stool in a sterile container|
Close the lid until it clicks|
Place the container on the middle shelf of the refrigerator (not in the door!)|
Deliver to the laboratory within 2-6 hours (check with the clinic)|
Do not use the freezer-->
🔍 Tip: If you have a refrigerator with a No Frostsystem, avoid storing the container near the ventilation openings - cold air flows can locally reduce the temperature below +4°C. In models with freshness zones (for example, Samsung Twin Cooling Plus or LG DoorCooling+) it is optimal to use compartment marked "0°C" or "Fresh Balancer".
What happens to feces during long-term storage in the refrigerator
When the permissible storage period is exceeded, processes are launched in feces that make the analysis inaccurate:
- 🦠 Death of anaerobic bacteria (for example, Bifidobacterium, Bacteroides) - their number in the sample decreases by 30–50% after 12 hours.
- 📈 Reproduction of facultative microbes (for example, E. coli, Enterococcus) - their share is artificially increased.
- 🧬 DNA decay some bacteria (relevant for PCR diagnostics), which leads to false negative results.
- 💧 Change consistency due to loss of moisture - this complicates the work of the laboratory assistant and can lead to errors during inoculation.
📊 Example: If in fresh feces the ratio Bifidobacterium and Lactobacillus was 10:1, then after 24 hours in the refrigerator it can shift to 5:1 or 3:1 - and the doctor will make an erroneous diagnosis of “dysbacteriosis.”
Why do laboratories not accept stool older than 24 hours?
When stored for more than a day, toxins accumulate in the sample (for example, indole, skatole), which inhibit the growth of some bacteria on nutrient media. In addition, autolysis (self-dissolution) of cells begins, which makes it impossible to identify them. microscope.
⚠️ Attention: If you stored stool for longer than the permitted period, do not try to “refresh” the sample by adding saline or water to it. This will lead to false dilution of the microflora and further distort the results. It is better to retake the analysis.
Temperature: what should it be in the refrigerator?
To store feces for dysbacteriosis, it is critical to maintain the temperature in the range +4…+8°CHow to check and set it up:
- 🌡️ Use a separate thermometer. Built-in refrigerator sensors (especially in models Indesit, Atlant budget line) can show the temperature with an error of up to ±2°C.
- ❄️ Adjust the cooling mode. In most refrigerators, the optimal setting is
3–4 divisionon the thermostat (or+4°Cin the electronic management). - 🚫 Avoid areas with temperature fluctuations:
- The refrigerator door (it is 2-3°C warmer there).
- The bottom shelf above freezer (can be colder than +2°C).
- Area next to the lamp (heats up when opened).
| Refrigerator area | Temperature, °C | Suitable for storing feces? |
|---|---|---|
| Top shelf | +6…+8 | Yes (if not above +8°C) |
| Middle shelf | +4…+5 | Ideal |
| Bottom shelf (above the freezer) | +2…+3 | No (risk of freezing) |
| Door | +8…+10 | No |
| Fresh zone (0°C) | 0…+1 | No (too cold) |
⚠️ Attention: If your refrigerator equipped with a function "Super cooling" or "Fast freezing" (for example, in models Bosch VitaFresh or Liebherr BioFresh), disable it while storing the analysis. A sharp drop in temperature can kill part of the microflora.
Frequent errors when storing feces and how to avoid them
According to laboratory statistics, 60% of patients make at least one of these mistakes:
- Storage in a leaky container container.
Consequences: the ingress of oxygen leads to the death of anaerobes (Bifidobacterium, Bacteroides).
Solution: check that the container lid closes until it clicks. If the container is damaged, use a new one.
- Using the wrong container.
Consequences: residues of detergents or fat on the walls of the jar inhibit the growth of bacteria.
Solution: buy only pharmacy sterile containers (cost 10–50 rubles).
- Storage next to products with a strong odor.
Consequences: volatile compounds (for example, from onions, garlic, fish) can penetrate the plastic and affect the biochemical composition of the sample.
Solution: place the container in a separate bag or on a distant shelf.
- Transportation without a coolant.
Consequences: if it is hot outside, the temperature is bag can rise to +15...+20°C, which will speed up reproduction E. coli i Staphylococcus.
Solution: use a thermal bag with a cold accumulator (sold in pharmacies).
🔍 Advice for parents: If the child passed stool in the evening, and the laboratory works only in the morning, place the container on the middle shelf of the refrigerator and wrap it in foil —this will protect against temperature changes when opening the door.
What to do if there is no way to quickly deliver the analysis
If you If you live far from the laboratory or are in a force majeure situation (for example, a transport collapse), use these methods:
- ❄️ Cooling element. Buy a cold accumulator at the pharmacy ("Snowflake", "Medicholod") and put it in your bag along with the container. This will maintain a temperature of +4°C for 4-6 hours.
- 🚗 Courier delivery. Many laboratories (for example, Hemotest, Citylab) offer the service of taking samples at home. The cost is 300–800 rubles, but this is guaranteed. compliance with all conditions.
- 🏥 Preservatives. Some clinics issue special tubes with a preservative (for example, Port-a-Cul), which preserves the microflora until 48 hours. Check in advance!
⚠️ Attention: If you are using a cold pack, do not place it directly on the container with stool - this can locally cool the sample to 0°C. It is optimal to place the cold pack next with the container, wrapping both in cloth. towel.
FAQ: Answers to frequently asked questions
Is it possible to store stool for dysbacteriosis in the freezer?
No! Freezing destroys the cell walls of bacteria, and the analysis will become uninformative. The exception is special studies (for example, for calprotectin), but for dysbiosis the freezer is needed. is unacceptable.
What will happen if you store stool for longer than 24 hours?
The results will be unreliable: some bacteria will die, while others will multiply. The doctor may mistakenly diagnose dysbacteriosis or, conversely, miss pathogenic flora.
Is it possible to collect stool in the evening and donate it? in the morning?
Yes, if you store it at +4°C for no more than 12 hours (for qualitative analysis, it is better to maintain an interval of 6–8 hours.
How does taking antibiotics affect the analysis?
Antibiotics distort the microflora, so the test for dysbacteriosis is taken no earlier than after 2 weeks after the end of the course (for some drugs, for example Ciprofloxacin, after 4 weeks).
Can a urine container be used for feces?
No! Urine containers are not airtight and are not intended for use. thick biomaterials. In addition, traces of salts or preservatives may remain on their walls.
If you have any doubts about storing or transporting the analysis, contact the laboratory in advance. Remember: the accuracy of the diagnosis depends on how strictly you followed the preparation rules.