How much amount of stool should be sampled for physical examination

Physical examination stool sampling generally requires a stool sample the size of a soybean (about 5 grams), which is approximately the volume of the first phalanx of the thumb. The sampling amount should cover different parts of the feces to avoid contact with urine or urinals. The sample size requirement for routine fecal examination is mainly based on the requirements of the testing items. About 5 grams of feces is sufficient to meet basic testing needs such as occult blood tests, parasite egg screening, and microbial culture. When sampling, a matching sampling spoon or cotton swab can be used to take a small portion from the surface and inside of the feces and mix them to ensure that the sample reflects the overall characteristics. If there are abnormal parts such as mucus and blood streaks in the feces, these areas should be prioritized for selection. A small sample size may lead to a decrease in detection sensitivity, but exceeding 10 grams does not improve accuracy and may instead increase the risk of contamination.

After sampling, it should be sent for testing within 1 hour to avoid prolonged storage that may cause bacterial growth or component degradation. If the testing item is special (such as genetic testing), the sampling amount needs to be adjusted according to laboratory requirements. The sampling of children's feces can be appropriately reduced to 3 grams, but the integrity of the sample still needs to be ensured.

Avoid consuming animal blood products, iron supplements, or other foods or drugs that may interfere with occult blood results 24 hours before sampling. Use a dry and clean container to hold the sample, avoiding mixing with toilet paper, water, or other foreign objects. If it is not possible to send the sample for testing immediately, it can be temporarily stored in a refrigerator at 4 ℃ for no more than 2 hours.