A stool sample, also known as a fecal sample, involves collecting a small amount of a person’s bowel movement for subsequent laboratory analysis. This diagnostic tool offers a window into the health of the entire digestive tract, allowing healthcare professionals to identify various gastrointestinal conditions.
Stool analysis plays a role in diagnosing a spectrum of issues, including infections caused by bacteria, viruses, or parasites. It can also reveal signs of inflammation, issues with nutrient absorption, or even early indicators of certain cancers, such as colorectal cancer. The information derived from these tests guides medical professionals in making diagnoses and determining treatment plans, helping to address symptoms like diarrhea, abdominal pain, or unexplained weight loss.
General Quantity Guidelines
The amount of stool necessary for a sample is not uniform and depends directly on the specific laboratory test requested. For many routine analyses, a small quantity is typically sufficient, often about 10 to 15 grams. This can be visualized as roughly one to two tablespoons or the size of a walnut. Some tests, such as those for Helicobacter pylori antigen, may require as little as a half teaspoon or a grape-sized amount.
Collection kits often provide clear fill lines or specific instructions, sometimes indicating to fill the container just under halfway. Following these directions precisely prevents both insufficient and excessive sample collection, which can compromise results. Overfilling a vial, for instance, can reduce the recovery of certain pathogens, impacting test accuracy. Always adhere to the specific guidelines from the healthcare provider or the collection kit, as these are tailored to the precise analytical requirements of the testing facility.
Factors Affecting Sample Size
The required sample size for stool testing fluctuates due to the diverse types of analyses performed and the specific substances or organisms being targeted. For example, tests that screen for occult (hidden) blood, such as the Fecal Immunochemical Test (FIT), typically need only a small amount, often a thin smear on a specialized card. This contrasts with stool cultures, which identify pathogenic bacteria like Salmonella or Shigella, often requiring a thumbnail-sized portion of stool for adequate microbial growth.
Detecting parasites, such as Giardia or Cryptosporidium, or their eggs, usually calls for a more substantial sample to increase the likelihood of finding these organisms, which may be present intermittently within the stool. Similarly, tests for Clostridium difficile toxin or comprehensive gut microbiome analysis often benefit from a larger volume for accurate diagnosis.
Proper Collection Techniques
Accurate stool sample collection requires strict adherence to hygiene protocols to prevent contamination. Before handling any materials, wash hands thoroughly with soap and warm water for at least 20 seconds, and consider wearing disposable gloves. It is also important to empty the bladder before collecting the stool, as urine can interfere with test results and contaminate the sample.
To ensure the stool does not touch the toilet water, which can invalidate the sample, several collection aids are available. Many kits include a “collection hat” that fits securely under the toilet seat, or a clean, wide-mouth container can be used. Another effective method involves loosely draping plastic wrap across the toilet rim to create a collection surface. For young children or infants, lining their diaper with plastic wrap can help collect the sample while keeping it separate from urine.
After the stool is passed, use the provided scoop or wooden stick to transfer the appropriate quantity into the specimen container. It is advisable to select portions of the stool that appear most representative, such as areas containing blood, mucus, or watery elements, as these can be particularly informative for certain analyses. Carefully transfer the sample, avoiding contact with the outside of the container, and ensure it is filled to the indicated line without overfilling. This maintains the proper balance with any preservatives and helps ensure accurate results.
Handling and Storage
After collecting the stool sample, proper handling and storage are essential to maintain its integrity and ensure accurate test results. Immediately after transferring the sample, securely fasten the container lid to prevent leakage. Labeling the container clearly with the patient’s full name, date of birth, and the exact date and time of collection is important, as laboratories rely on this information for accurate processing.
Temperature requirements vary; some samples need refrigeration (2-8°C or 36-46°F) if not immediately transported, while others in special transport media can remain at room temperature. Unpreserved stool samples should reach the laboratory as soon as possible, ideally within two hours, but often within 24 hours. If immediate delivery is not feasible, specific storage guidelines, such as placing the sealed container in a plastic bag before refrigerating, help maintain sample viability.