Testing for hidden blood, helminth eggs or A coprogram requires strict adherence to the rules for collecting and storing biomaterial. Many patients mistakenly believe that simply placing the container in the cold is enough, without thinking about the fact that temperature regime and location affect the chemical composition of the sample. Laboratory diagnostic doctors often receive defective material, the results of which cannot be interpreted due to violation of transportation conditions.
A refrigerator is not just a cabinet for food, but a complex system with an uneven distribution of temperature zones. Depending on where exactly you place the container with the biomaterial, the rate of chemical reactions inside it may change. For example, on a shelf near the back wall the temperature can drop below zero, which will lead to partial freezing and destruction of cellular structures, making analysis for dysbacteriosis or protozoa pointless.
In this article we will look in detail at how to properly prepare the container, where exactly it is best to put it and how long it is allowed to store the sample before delivery to the laboratory. Following these recommendations will allow you to avoid repeated testing and get a reliable result the first time.
Why the correct temperature is important
Biological samples, such as feces, urine or sputum, are unstable environments. The vital processes of microorganisms continue to occur in them even after defecation. If the correct conditions are not provided, bacteria will begin to actively multiply, changing the pH of the environment and destroying the very pathogens that need to be detected. That is why storage at room temperature is allowed only for a short time. cooling, bacteria will begin to actively multiply, changing the pH of the environment and destroying the very pathogens that need to be detected. That is why storage at room temperature is allowed only for a short time.
The optimal temperature for preserving the properties of the biomaterial varies from +2 to +8 degrees Celsius. This is the standard mode of operation of the refrigerator compartment, but it may differ in different parts of the refrigerator. A temperature that is too low will cause water to crystallize in the cells, rupturing their membranes, while a temperature that is too high will speed up fermentation.
For different types of research, the requirements may vary slightly. For example, the analysis of na occult blood is more sensitive to oxidative processes, while the search for worm eggs requires preserving the morphology of the parasites' membranes. Violation of the temperature regime can lead to a false negative result when the disease is present, but the analysis does not show it.
The key factor stability is here. Sudden changes in temperature, such as if you frequently open the door or place a warm container next to the freezer, are detrimental to the sample. The biomaterial must cool gradually and evenly, maintaining its original properties throughout the entire time before the study.
The ideal place for the container in the refrigerator
The choice of a specific shelf or compartment of the refrigerator is not a matter of convenience, but a matter of cold air physics. Cold air is heavier than warm air, so it sinks, but evaporators are usually located at the back wall, where the temperature is minimal. Placing a container with feces directly at the back wall or on the top shelf at the cold air outlet is strictly not recommended.
The most suitable place is the middle or bottom shelf of the main chamber, but always at the front wall or on the door (if there is an area for medications, although this is not always ideal due to differences when opening). The refrigerator door is an unstable area, the temperature there often rises above +8 degrees with frequent use, which can be risky for long-term storage.
⚠️ Attention: Never leave a container with biomaterial in the freezer! Freezing completely destroys the cellular structure of protozoa (giardia, amoeba) and makes microscopy impossible.
It is best to use the zone freshness (zero chamber), if it is in your refrigerator and maintains a temperature of about 0...+2 degrees, but only if there is no risk of freezing there. However, the classic lower shelf of the main compartment, away from the compressor and door, remains the gold standard.
It is also important to consider the proximity. The container should be hermetically sealed, but storing it next to open food, especially meat or fish, is unhygienic. Use a separate plastic container or bag to isolate the medical sample from food products.
Preparation of the container and collection of material
The quality of the analysis directly depends on how the material is collected. Pharmacy containers are made of inert plastic that does not react with stool components. The use of homemade jars, matchboxes or plastic bags is unacceptable, as they may contain impurities that distort chemical analysis chemical analysis.
The collection process also requires cleanliness. Before defecation, it is necessary to prepare a clean surface (a potty, a thoroughly washed bedpan, or a plastic film stretched over the toilet). Contact with water from the toilet or detergents should be completely excluded, since chlorine and other reagents kill microflora.
☑️ Rules for collecting feces
The volume of material for research is usually small. It is enough to collect an amount equal to one teaspoon or 5-10 grams. If there are visible impurities in the stool (mucus, blood, pus), they must be captured, since this is where the concentration of pathogens is maximum. Occult blood testing may require special dietary restrictions for 3 days prior to collection.
Immediately after collection, the container should be closed and placed in a cool place. If you collect material in the evening for the morning submission, time is against you. The faster the sample is in the conditions stable cold, the more accurate the result will be.
Storage life of the biomaterial
Time is a critical resource when working with analyses. There is a myth that stool can be stored in the refrigerator for days, but this is not true. For most standard studies (coprogram, helminth eggs, protozoa), the storage period should not exceed 8-12 hours. Ideally, deliver the material to the laboratory within 2 hours after defecation.
Some types of tests, for example, for dysbiosis or intestinal group, require even faster delivery - up to 1-2 hours. Bacteria outside the body quickly change their composition, and after 4-5 hours the sample may no longer be dominated by those microorganisms that lived in the intestines, but by those that multiplied in the container.
The table below shows the dependence of the shelf life on the type of study:
| Type of analysis | Maximum period at room temperature t° | Maximum period in the refrigerator (+2...+8°C) | Features |
|---|---|---|---|
| Coprogram | Up to 2 hours | Up to 12 hours | Overnight storage is allowed |
| Eggs of worms | Up to 1 hour | Up to 8-10 hours | Larvae can hatch |
| Hidden blood | Not recommended | Up to 6-8 hours | Diet required before donation |
| Dysbacteriosis | No more than 30 minutes | Up to 2-3 hours | Only fresh material |
If you do not have time to deliver the analysis within the specified time, it is better to reschedule the visit to the laboratory for another day and collect fresh material. Donating “old” stool can lead to an erroneous diagnosis and unnecessary treatment.
What absolutely should not be done
There are a number of common mistakes that ruin all efforts to collect analysis. The first and most common is adding water. Under no circumstances should you dilute stool with water or use wet wipes for collection, as this changes the density and chemical composition of the sample.
The second mistake is keeping it warm. A container left on a table or windowsill becomes an ideal breeding ground for putrefactive bacteria. Even if it is winter outside, the temperature in the room near the heating radiator may be too high to preserve the biomaterial.
⚠️ Attention: Do not use the freezer or the “super-freezing” mode to store the biomaterial. Ice crystals will damage the shells of parasite eggs and epithelial cells.
Also, you should not store the container open. Evaporation of moisture will cause the sample to dry out, making it impossible to prepare a high-quality smear for microscopy. The tightness of the lid is a prerequisite.
Ignoring the rules of hygiene during collection (ingress of urine, menstrual blood or water) also refers to gross violations. This can simulate an inflammatory process or, conversely, hide its signs.
Transportation to the laboratory
Properly storing the material at home is only half the battle. It is important to deliver it to the laboratory correctly. During the warm season, the temperature difference when leaving the house can be critical. Use thermal container or a regular cooler bag if the travel time exceeds 20-30 minutes.
You must have a doctor's referral and a passport with you. The container must be marked (full name, date and time of collection) so that there is no confusion at the register. Some laboratories require filling out special forms that can be downloaded on their website in advance.
What to do if there was no stool in the morning?
If the test needs to be taken strictly in the morning, but there is no bowel movement, you can try to stimulate the process naturally (light exercise, a glass of water on an empty stomach). Enemas and laxatives cannot be used - they distort the result. As a last resort, agree with your doctor on the possibility of collecting material in the evening of the previous day.
Laboratory staff can also give additional recommendations based on specific test requirements. For example, to test for carbohydrates, stool must be delivered within 30 minutes, since the enzymes continue to work even when cooled.
Remember that the laboratory technician sees the sample as you brought it. Your task is to minimize changes that have occurred outside the body so that the diagnosis is accurate.
Storage features for children and infants
Collecting analysis from infants is a separate topic that raises many questions among parents. For babies, there are special urine bags and sterile spoons that allow you to carefully collect material from the surface of the diaper (but not from the absorbent layer!).
It is important to understand that feces taken from a diaper with gel filler are not suitable for analysis. The gel absorbs the liquid fraction, leaving only dense particles, which disrupts the ratio of elements. You need to collect it from a clean oilcloth or sterile diaper immediately after defecation.
The shelf life for children's feces is as strict as for an adult. However, in infants, fermentation processes go even faster due to their feeding habits (breast milk or formula). Therefore, the rule “the faster, the better” works squarely here.
If the child is taking any medications, especially antibiotics or drugs bismuth/iron, you must warn the doctor and laboratory assistant about this, as this can color the stool or change its chemical properties.
Is it possible to collect stool for analysis in the evening if the laboratory works only in the morning?
Yes, for some types of research (coprogram, worm eggs) it is allowed to collect material in the evening. In this case, the container must be tightly closed and immediately placed in the refrigerator on the bottom shelf. The period of such storage should not exceed 8-10 hours. For tests for dysbacteriosis and occult blood, evening collection is not recommended.
What to do if stool is frozen in the refrigerator?
If the biomaterial has been frozen, it cannot be used for analysis. Ice crystals destroy the cellular structures of protozoa and helminth eggs, making them invisible under a microscope. Such a sample is considered defective, and the analysis will have to be retaken.
Is it necessary to sterilize the container before collection?
There is no need to specially sterilize the container with boiling water if you use a sterile pharmacy cup. It is enough to keep it dry and clean. Water inside the container is unacceptable, as it will wash away useful elements and distort the result.
Does menstruation affect the result of stool analysis?
Yes, it does. Even a small amount of blood from the genital tract in a stool sample may give a false positive result for occult blood. Women are advised to take a test either before the start of menstruation, or after it ends, or use a tampon when collecting it to prevent secretions from getting in.