Submission of laboratory tests is a standard procedure that every person who monitors their health faces. However, the accuracy of the result depends not only on the professionalism of the laboratory technicians and the quality of the equipment, but also on how correctly the biomaterial was collected and delivered. Freshness of the sample is a critical factor, especially when it comes to coprogram or searching for worm eggs.
Situations often arise when delivering the container to the laboratory immediately after defecation is physically impossible. For example, the test is scheduled for early in the morning, and the child wakes up only an hour after the parents leave the house, or the reception center works according to a strict schedule. In such cases, the only option is to store the material at home. A logical question arises: how long can a sample be left at low temperatures so that it does not lose its diagnostic properties?
The answer to this question is ambiguous and depends on the type of study, since different microorganisms and chemical compounds behave differently in the external environment. Enzyme activity bacteria in the sample does not stop instantly, even if you place it in the cold. It is the processes of decomposition and changes in the chemical composition that are the main enemies of accurate diagnosis, therefore the temperature regime and time intervals should be treated with maximum attention.
Why does the storage time of biomaterial matter
Feces are a complex mixture of undigested food debris, bacteria, epithelial cells and products vital activity of the body. Immediately after leaving the intestine, active biochemical processes begin in the sample. Bacteria continue to multiply, and enzymes continue to break down organic matter. If these processes are not stopped or slowed down, the composition of the sample will begin to change, which will lead to distorted results.
Change in pH environment and the destruction of the cellular structures of leukocytes or red blood cells occurs faster than most patients think. For example, when testing for occult blood, long-term storage may give a false-positive result due to hemolysis of red blood cells. At the same time, when searching for the simplest microorganisms, such as Giardia, a delay in delivery can lead to the fact that the mobile forms turn into cysts or are destroyed, and the laboratory technician simply does not see the pathogen.
⚠️ Attention: Biomaterial collected more than 24 hours ago, even with ideal cooling, in most cases considered unsuitable for research. Don’t try to take “yesterday’s” analysis, hoping for a miracle - you will waste your money and time.
There is a misconception that the freezer can preserve a sample forever. This is wrong. Freezing causes water to crystallize inside the cells, causing them to rupture. After defrosting, the structure of the sample will be completely destroyed, and microscopic examination will become impossible. Therefore low temperatures in the refrigerator (not freezer) they only slow down the processes, but do not stop them completely.
General rules for collecting and preparing the container
The quality of the analysis is established at the collection stage. To do this, you must use a special sterile container. Glass jars for baby food or mayonnaise, even thoroughly washed, are not recommended, since microparticles of detergents or organic residues may remain on their walls, which will affect the chemical composition of the sample.
The defecation process should take place in a clean container. Do not collect material directly from the toilet, even if it appears clean, as the water may contain chlorine, bacteria or other contaminants. The best option is to use a special vessel, a potty for children, or a clean plastic film stretched over a toilet seat.
- 📦 Use only sterile plastic containers with a screw cap, purchased at a pharmacy.
- 🚽 Avoid getting urine, toilet water, or menstrual fluid into the sample discharge.
- 🥄 Take the material with a special spoon built into the lid from 3-4 different places in the feces.
Particular attention should be paid to the volume of collected material. For most studies, a volume equal to one or two teaspoons is sufficient. If too little is collected, the laboratory technician may not have enough substance to carry out all the necessary reactions. If you fill the container to the brim, when opening the lid in the laboratory, you may break the sterility or get dirty.
Storage periods for different types of analyzes
The time that the biomaterial retains its properties directly depends on the purpose of the study. Different pathogens and chemical markers have different resistance in the external environment. Therefore, there is no universal answer “how long can you store” - you need to look at the doctor’s direction.
During coprogram (general analysis), physical properties, the presence of mucus, blood, undigested food and muscle fibers are assessed. Here the requirements are the most stringent, since macroscopic changes begin quickly. The time frame for detecting helminth and protozoan eggs is also limited, although some parasitological schools allow storage in preservatives.
If we are talking about bacteriological culturethen there are rules. Often these tests require delivery in special transport media that allow the bacteria to survive and even reproduce in transit. It is extremely undesirable to store regular stool for culture for dysbacteriosis or intestinal group in the refrigerator, since the ratio of aerobic and anaerobic flora may change.
Below is a table systematizing the permissible storage time for the main types of research, provided that the sample is in the refrigerator.
| Type of analysis | Maximum period in the refrigerator | Optimal delivery time | Frozen permissibility |
|---|---|---|---|
| Coprogram (general) | Up to 8 hours | 2-3 hours | Strictly prohibited |
| Eggs of worms (helminths) | Up to 24 hours (in preservative) | Up to 5-6 hours | Not recommended |
| Occult blood | Up to 6-8 hours | Immediately | Prohibited |
| Bacteriosis (dysbacteriosis) | No more than 2-3 hours | Instantly | Prohibited |
Temperature conditions and conditions in the refrigerator
When we talk about storage in the refrigerator, we mean a certain temperature. The standard temperature in the main chamber of a household refrigerator is from +2 to +6 degrees Celsius. It is this range that makes it possible to inhibit the proliferation of bacteria without causing destruction of cellular structures, as during freezing.
Where exactly should the container be placed? Many people make the mistake of leaving material on the door. This is the warmest place with frequent temperature changes with each opening. Ideal zone —the middle shelf or lower part of the main chamber, away from the back wall, where it may be too cold, and from the door.
⚠️ Attention: It is strictly forbidden to store biomaterial in the freezer! Ice crystals will rupture the epithelial cells and membranes of the protozoa, which will make the analysis pointless. Also, you should not leave the container on a windowsill or near heating devices.
It is important to ensure the tightness of the packaging. The smell from the container can be absorbed into the food lying nearby, which is unhygienic. Additionally, foreign odors could theoretically interfere with some types of chemical tests, although this is less likely. It is best to place the closed container in a clean plastic bag.
What to do if the refrigerator is broken?
If the electricity in the house is turned off or the refrigerator has stopped cooling, and you need to get tested urgently, use “cold”. Wrap the container in several layers of cloth and place it in the coolest place possible (for example, on the floor against an outside wall in winter or in the shade). However, the shelf life under such conditions is reduced to 1-2 hours maximum.
Is it necessary to use preservatives
In some cases, doctors may recommend collecting the material in special preservatives. These are chemicals that lock in the structure of parasites or bacteria, allowing the sample to be stored longer. Most often, this is required for complex parasitological studies, when delivery to the laboratory takes a long time.
Add alcohol, formalin or other chemicals to the stool yourself absolutely not. You can completely destroy the microflora or change the chemical reaction, which will lead to a false diagnosis. Preservatives are used only in special pharmaceutical containers intended for specific types of tests (for example, containers with Safaraliev solution).
If you use a container with a preservative, strictly follow the instructions on the package. Typically, such systems allow the material to be stored for up to 2-3 days at room temperature or in the refrigerator, but this depends on the type of preservative. For a standard coprogram, preservatives are not used.
Features of collection in children and bedridden patients
Collecting analysis in young children often turns into a quest. Infants do not know how to endure on command, and older children may be afraid of the process. For infants, it is convenient to use urinals attached to the skin around the anus, or to collect material from a clean oilcloth while the child is lying on his stomach.
Stimulation of defecation a gas outlet tube or an enema is permissible only as prescribed by a doctor and in extreme cases, as this can damage the mucous membrane and distort the result (blood or mucus will appear). It is better to wait for a natural urge.
- 👶 In infants, you can collect material from the diaper, but only from the surface, without touching the absorbent layer (it will absorb the liquid and change the composition).
- 🚽 For potty-trained children, the potty should be thoroughly washed and pour boiling water over before use.
- 🛌 For bedridden patients, the material is collected from a clean vessel or special spoons are used after defecation in a diaper (from the surface).
☑️ Checklist before taking the analysis
If the child goes to the potty, make sure that he has not peed before. Urine should not be mixed with feces. If this happens, you will have to collect the material again, since uric acid and other components of urine destroy the structure of feces.
Frequent errors during transportation and storage
Even if you correctly collected the material and placed it in the refrigerator, errors can await you at the transportation stage. In the summer heat, biomaterial can deteriorate while you are driving it in a traffic jam. In winter, on the contrary, the sample can become hypothermic if it is carried in a bag without a thermos.
One of the common mistakes is using dirty containers. Even traces of old feces in a poorly washed (but not sterile) jar can contain protozoan cysts or worm eggs, which will give a false positive result. Always use disposable pharmacy containers.
⚠️ Attention: Do not leave the container with biomaterial in the car in direct sunlight or near a working stove. Heating above +20 degrees sharply accelerates the processes of fermentation and rotting.
Also, patients often forget to sign the container. In high-traffic laboratories, plug mix-ups are not uncommon. The marker must be durable so that the inscription is not erased by condensation in the refrigerator or in the hands.
Is it possible to take a stool test if it has been in the refrigerator overnight (8-10 hours)?
For a general analysis (coprogram) and searching for occult blood, such a sample will most likely be rejected or give a distorted result. The enzymes have already started working, the pH has changed. For analysis of worm eggs (helminths), overnight storage (up to 10-12 hours) is allowed in some laboratories, but only if tightly closed and at a temperature of +4...+6°C. However, it is better to clarify this point with the laboratory technician of a particular clinic, since the requirements may differ.
What to do if mucus or blood is found in the stool?
If you notice visible inclusions of mucus, pus or blood, be sure to take material for analysis from these places. Use a spoon to scoop out the suspicious area. It is there that the concentration of pathogenic microorganisms or inflammatory marker cells will be maximum, which will increase the information content of the study.
Does taking medications affect the result of the analysis?
Yes, many drugs can distort the picture. Antibiotics affect bacteria and coprogram. Bismuth and iron preparations turn stool black, which can mimic melena (black stool when bleeding) or interfere with the chemical reaction to occult blood. Laxatives and enemas make the test for occult blood and coprogram unreliable. You should tell your doctor about any medications you are taking.
Can you store stool in a container with a cotton swab?
No, such containers are usually intended for swabs (for example, from the throat or nose) or for rectal collection of material, but not for storing formalized stool. For stool you need a sealed plastic cup with a spoon. Cotton wool can absorb the liquid fraction, disrupting the ratio of elements, or dry out, making it impossible to prepare a smear for microscopy.
How to sign the container correctly?
Use a permanent marker. On the lid or in a special field (if there is one), write: Last name of I.O., date of birth (or age) and, most importantly, the date and exact time of collection of the material. Time is important for the laboratory technician to assess the suitability of the sample. It is better not to use stickers with printed data, they can come off due to condensation.