Collecting biological material for laboratory research often becomes stressful for parents, especially when it comes to young children. The child’s body works according to its own biological clock, and the moment of defecation may occur at the most inopportune time, for example, late at night or early in the morning, when laboratories are still closed. In such situations, moms and dads are faced with the acute question of the possibility of preserving the sample until delivery to a medical facility.
The quality of diagnosis directly depends on how fresh the material was at the time of the study. Parasites, their eggs and larvae are sensitive to changes in the external environment, and failure to comply with transportation rules can lead to a false negative result. This means that the disease will remain undetected, and the child will not receive the necessary treatment, which is fraught with further spread of the infection in the team or family.
In this article we will look in detail at how to properly organize the storage of biomaterial, what temperature conditions are acceptable and why refrigerator often becomes the only salvation for parents. We will look at the time intervals during which the analysis remains informative and discuss the nuances associated with different types of parasites.
Why the time of delivery of biomaterial is critical
The main purpose of laboratory stool analysis is the detection of helminth eggs, their larval forms or adult fragments individuals. Immediately after defecation, active destruction processes begin in the sample, which can make parasites invisible to the microscope. The enzymatic activity inherent in the intestinal contents continues to work outside the body, gradually changing the structure of the material.
Some types of protozoa, such as amoebas or lamblia, are mobile in their native (fresh) form, which is a diagnostic sign. However, when cooled or stored for a long time, they lose mobility, become rounded, and can be mistaken for epithelial cells or leukocytes by a laboratory assistant. That is why sample freshness is a key factor in the successful diagnosis of protozoal infections.
For worm eggs, the time factor also plays a role, although they are more stable in the external environment. Long-term storage, especially at the wrong temperature, can lead to deformation of the egg shells or their destruction. If the laboratory technician does not see characteristic signs of parasites due to deterioration of the material, the diagnosis will not be confirmed and treatment will not be prescribed.
⚠️ Attention: Material collected after using an enema or taking laxatives, as well as after an X-ray examination with barium, is unsuitable for analysis. This may distort the picture of the study and lead to an erroneous diagnosis.
There is a common misconception that if you place the container in the cold, then the time at which biological processes stop does not matter. This is wrong. Even at low temperatures, irreversible changes occur in the structure of cells and organisms, therefore maximum period storage is still limited and must be strictly observed.
Optimal storage periods depending on the purpose of the analysis
The answer to the question of how long feces can be stored depends on what exactly the research is being conducted on. Different types of parasites and diagnostic methods dictate their own time frames. For most standard tests for eggs of worms (helminth infections) and protozoa, certain rules apply, violation of which reduces the reliability of the result.
Under ideal conditions, when the material is delivered to the laboratory warm, no more than 1.5–2 hours are allotted for the study. However, in the realities of life with a child, this is often impossible. If you are forced to store a sample, then at a refrigerator temperature (from +2 to +4 degrees Celsius) a period of up to 8 hours is considered acceptable. In some cases, when using special preservatives, this period may be extended, but the doctor must tell you about this.
It is important to understand the difference between an analysis for worm eggs and an analysis for enterobiasis (scraping for pinworms). For the latter, the material is collected differently - using adhesive tape or a cotton swab from the surface of the skin around the anus. Such material should be stored in the refrigerator absolutely not, it must be delivered to the laboratory within 2 hours, since pinworm eggs quickly lose their properties and may fall off or collapse.
If you collected the material in the evening, and an appointment with a doctor or delivery to the laboratory is possible only in the morning of the next day, try within the 8-hour window. For example, if a bowel movement occurred at 10:00 pm, then the container should be delivered no later than 6:00–7:00 am. Exceeding this time significantly reduces the chances of detecting parasites.
Rules for collection and packaging for long-term storage
In order to maximize the information content of the sample until delivery, it is necessary to properly organize the collection process. Using unsuitable containers can lead to drying out of the material, the ingress of foreign impurities, or the growth of bacteria, which will make it difficult for the laboratory technician to work.
To collect stool, use only sterile plastic containers with a tight-fitting lid, which are sold in pharmacies. Such containers are airtight and do not allow odors to pass through, which is especially important when stored in the refrigerator next to food. Glass baby food jars can be used, but only after thorough sterilization, although the risk of chipping and a less tight fit of the lid makes them less preferable.
☑️ Rules for collecting material
When collecting material, it is important to take samples from different areas of feces - from above, from the side, from the inside. The volume of material should be approximately equal to the volume of one or two walnuts (about 5–10 grams). If the stool is liquid, carefully pour it into the container, being careful not to stain the walls and threads of the lid to ensure a tight seal.
Do not allow urine or toilet water to get into the sample. To do this, the child needs to be placed on a clean potty, previously washed with soap and rinsed with boiling water, or put cling film over the rim of the toilet bowl. The use of newsprint or diapers with pile for collection is not recommended, since fibers can get into the analysis and be mistaken for parasites.
Temperature conditions and conditions in the refrigerator
The main condition for preserving biomaterial is a stable low temperature. It slows down the processes of fermentation and bacterial growth, but should not lead to freezing. The optimal place in the refrigerator is the middle shelf, where the temperature is kept around +4°C.
It is strictly forbidden to freeze feces for analysis. Ice crystals formed during freezing destroy the cell membranes of helminth eggs and the parasites themselves. After thawing, the material becomes unsuitable for research, and the collection procedure will have to be repeated. Therefore, place the container away from the freezer and cooling systems.
| Parameter | Recommended value | Permissible deviation |
|---|---|---|
| Storage temperature | +2... +4 °C | up to +8 °C (no more than 2 hours) |
| Maximum period | 6-8 hours | up to 12 hours (reduced accuracy) |
| Place in the refrigerator | Middle shelf | Door (not recommended) |
| Freezing | Prohibited | Unacceptable |
Storing the container on the refrigerator door should also be avoided. Each time the door is opened, the temperature there fluctuates sharply, which can negatively affect the safety of the sample. It is best to place the container in a separate plastic tray or bag to prevent direct contact with other products, even if the lid is tightly closed.
Can I add preservatives myself?
Independent addition of chemicals, glycerin or saline without a doctor’s prescription is prohibited. This can completely change the chemical composition of the sample and make analysis impossible. Preservatives are used only in special transport media, which are issued in the laboratory for a specific type of research (for example, the preservation method).
Features of diagnostics in children of different ages
Collecting analysis from an infant and a preschooler has its own characteristics that affect the possibility of storing the material. Infants defecate frequently, and it is easier to catch the right moment, but the consistency of their stool is often liquid, which requires special care when pouring into a container.
Breastfed children are characterized by yellow stool with a sour odor, which quickly changes its properties upon contact with air. Such material must be delivered to the laboratory as quickly as possible, ideally within 2 hours. If this is not possible, storage in the refrigerator is acceptable, but it is better to reduce the period to 4–5 hours.
In older children, the feces are more shaped, which makes it easier to collect and store. However, a psychological factor may play a role: the child may be embarrassed or afraid of the procedure, which will lead to constipation or, conversely, diarrhea from stress. In such cases, it is important to reassure the child and not force him, since stressful stools may also be less informative.
If the child is being treated with antibiotics or other drugs that affect the microflora, this must be reported to the doctor. Medicines can change the color, consistency and smell of feces, as well as affect the viability of parasites, which requires a special approach to interpreting the results.
Common mistakes when preparing for analysis
Even knowing the theoretical rules, parents often make practical mistakes that nullify all efforts. One of the most common is collecting material the night before, “just in case,” when the child has not yet gone to the toilet, or storing the collected sample for more than a day, “just in case.”
Another mistake is using unsterile containers. Jars of medicines, spices or cosmetics may contain residues that will react with feces. Even a thoroughly washed jar with water can contain microparticles of detergent that will kill protozoa or change the reaction of the environment.
Some parents try to “improve” the visibility of parasites by adding water to dense feces. You can't do this. Water causes the eggs to swell and can cause them to rupture, and also changes the specific gravity, which is important for flotation methods used in laboratories.
⚠️ Attention: Do not store the test container at room temperature if it takes more than 1 hour to get to the laboratory. In the summer or in a hot room, the processes of rotting and fermentation accelerate significantly, making the sample unusable after 30-40 minutes.
Forgetting to sign the container is also a common mistake, especially if several people in the family are tested or the child visits the kindergarten, where periodic testing is required. The container must have your last name, first name, date and time of collection. Without this marking, the laboratory may refuse to accept the material.
Interpretation of results and retesting
Having received the test result, parents often face a situation where no worm eggs are found, but the symptoms persist. This may be due to the fact that the parasites did not lay eggs at the time of collection, or the material was spoiled during storage. The life cycle of many helminths is cyclical, and they do not release eggs every day.
In this regard, a single negative result does not always mean the absence of infection. Doctors often recommend taking the test three times at intervals of several days. This allows you to “catch” the moment of active reproduction of parasites and increase the reliability of diagnosis to 90-95%.
If you suspect that you have violated the storage rules (for example, the container fell, the lid was slightly opened, or the material was kept warm), it is better not to take it to the laboratory, but to collect a new one. Researching low-quality material is a waste of time and money, as well as the risk of missing a serious disease.
Remember that timely and correct diagnosis is the key to the health of your child and the peace of mind of the whole family. Following simple rules for collecting and storing stool will help you get an accurate result and, if necessary, quickly begin effective treatment.
Is it possible to donate stool if a child has taken charcoal or bismuth?
Bismuth preparations and activated carbon color stool black, which can make a visual assessment difficult for a laboratory technician, but does not affect the detection of eggs worms under a microscope. However, carbon is a sorbent and can (absorb) some elements, so if possible it is better to wait 2-3 days after taking sorbents before taking the test.
What to do if white threads or worms are visible in the stool?
If you visually detect parasites in the stool, be sure to place them in a container along with the main material and report this to the laboratory assistant. Such findings often make it possible to identify the helminth species faster and more accurately than searching for microscopic eggs. Take a photograph of the find in good lighting before placing it in the container.
Do you need to wake up the child at night to collect the analysis?
There is no need to specially wake the child if he sleeps peacefully. The stress of waking up can cause spasms and make it difficult to have a bowel movement. It is better to wait for natural awakening or morning feeding, which often stimulates bowel movements in babies. If the bowel movement occurred at night, great, collect the material and put it in the refrigerator.
Does the diet the day before affect the test result?
A special diet is not required before testing feces for worm eggs. However, you should avoid foods that cause severe gas, diarrhea or constipation, as well as coloring foods (beets, blueberries), which can change the color of your stool. Eating plenty of fatty or protein foods may change the consistency, but will not hide the presence of parasites.