How to take a patient sample for testing?

The article was professionally consulted with Master, Doctor Tran Thi Vuong - Doctor of Microbiology - Laboratory of Laboratory - Vinmec Hai Phong International General Hospital.

Sample collection for testing is a technique to take a quantity of blood, secretions, waste or tissue from a patient and transfer to the laboratory. The test results are very important in the diagnosis, treatment and care of the patient.

The accuracy of test results is highly dependent on specimen collection, storage and transportation procedures. Therefore, it is necessary to pay attention to and follow the method of taking samples and handling samples for testing to get the most accurate test results.
1.1. Principles of specimen collection The collection of patient samples for testing is extremely important, determining the quality of patient samples in histopathological and cytological testing, greatly influencing the diagnostic results. Whether it is a cell sample, a fluid sample or a tissue sample, when taking a patient sample, it is necessary to ensure the following factors: Getting right and taking enough.
Get the right: Take the specimen in the right area of ​​the lesion Get enough: Get enough components, enough number of specimens needed for diagnosis. Commonly collected patient samples are blood samples, nasal fluid, nasopharyngeal fluid, oropharyngeal fluid, nasal lavage fluid, gargle, bronchial fluid, alveolar fluid, sputum, cerebrospinal fluid, endotracheal fluid, and fluid. Rectal smear, stool, semen, urine, saliva, blisters, skin biopsies.
Particularly for microbiological test specimens, there are additional principles:
Take samples at the right time Take them to ensure sterility with specimens in a sterile location Take samples before using antibiotics Send to patients products to the laboratory as soon as possible, within 2 hours. 1.2 Taking blood samples Depending on the purpose of testing such as biochemistry, hematology or blood culture, a separate sample container and sample tube will be required. For example, when taking blood for a complete blood count test, it is necessary to take it into a purple tube with EDTA anticoagulant, biochemistry and microbiological immunity, use a Heparin anticoagulant tube, and blood culture for bacteria, it is necessary to take blood into a culture bottle. specialized blood.

1.3 Take a sample of nasopharyngeal secretions Step 1: Ask the patient to sit still, slightly facing up. If you are a child, you need an adult to take care of you.
Step 2: The person taking the specimen tilts the patient's head back about 70 degrees, supporting the back of the patient's neck.
Step 3: With the other hand, gently put the cotton swab into the nose, push and rotate the cotton swab slightly about 1/2 length from the tip of the nose to the earlobe on the same side. Hold the swab at the sampling site for 5 seconds to obtain maximum infiltration.
Step 4: Slowly rotate and pull out the cotton swab. Place the impregnated cotton swab into a tube containing 3 ml of transport medium and store it.
1.4 Sampling endotracheal fluid Step 1: Only applicable to patients who are mechanically ventilated and intubated
Step 2: Use a suction tube placed through the endotracheal tract, and use a syringe to aspirate the endotracheal fluid according to the installed pipeline.
Step 3: Transfer endotracheal fluid into a plastic tube containing virus transport medium.
1.5 Collect rectal swab and stool sample Step 1: Ask the patient to lie on their left side, with thighs close to the abdomen.
Step 2: Wet cotton swab with sterile saline, insert cotton swab over anal sphincter and gently rotate.
Step 3: Pull out the cotton swab and check to make sure the tip is covered with stool. If the stool is thick, take about 4-5g (with the tip of your thumb), if it is liquid, take about 5ml of the specimen.
Step 4: Place the cotton swab in the tube containing the transport and storage medium. Note: Remember to break the top of the cotton swab so as not to touch the tube and firmly screw the button
1.6 Take a sample of the cerebrospinal fluid In particular, a sample of cerebrospinal fluid must be sampled by a medical professional with many years of experience. Cerebrospinal fluid will be collected directly into tubes with vortex caps. Usually at least 0.5 ml of CSF is required in one tube and collected in 3 separate tubes.

1.7 Urine Sampling Step 1: The patient is given specific instructions on how to collect a urine sample. Patients should wash their external genitalia with soap, saline or clean water before sampling.
Step 2: Use a urine collection bottle and collect urine only a few seconds after starting. The patient urinates directly into the plastic vial, avoiding touching the inside or rim of the plastic vial.
Step 3: The medical staff label the urine container. Make sure the urine container will not leak.
1.8 Remove blisters, scabs on the skin For skin scabs, the medical staff removes the skin from the lesion (ulcer) and transfers it to Phosphate buffered saline (PBS) or physiological saline.
For fluid at burn spots, staff follow these steps:
Step 1: Use cotton swabs soaked in alcohol to gently wipe the skin around the burn spots.
Step 2: Break the blisters or gently rub the tip of a cotton swab, take a sample of the border or bottom of the lesion.
Step 3: Place the swab with the specimen in the transport medium, tighten the cap, and store.
After taking the patient sample for testing, it is necessary to write the full name, age, bed number, and department name in the patient's specimen container before sending to the laboratory. Then the medical staff records information on the medical record including: date, time of technical practice, patient's condition before, during and after performing the technique, signing for confirmation.

After taking a specimen, the specimen should be preserved according to the correct procedure because if it is stored incorrectly, it may affect the test results.
Specimen smear cells need to be completely dry before shipping, to avoid mold and dirt on the slide, especially the slide with the specimen. It is recommended to use a stainless steel box with grooves to fix the two ends of the slide, to avoid breakage and impact during transportation. Glass slides and patient vials need to be properly affixed with the correct code, full of identification information to avoid confusion. Specimens should be stored in impact-resistant vials with lids to prevent spillage and loss of specimens. There is no need for formol fixation if the smear is taken within 12 hours. If the specimen is stored in the refrigerator at 2-4 degrees Celsius, it can be kept within 72 hours. If long-term preservation is required, it can be fixed with 50% Ethanol at a ratio of 1:1 depending on the volume. Specimens that are tissue samples (biopsy or surgical specimens) also need to be fixed with formol immediately after collection. Formol helps to penetrate quickly into the tissues and cells, helps to preserve or change only a little the basic structure of the organization and cells, resists destruction by intracellular enzymes and fights infections.

The collection and sampling of patient samples must ensure the safety of the sampler, the person being sampled, medical staff and people around. Before carrying out sampling, it is necessary to prepare appropriate sampling equipment, confirm and complete patient information.
3.1 Ensure safety of samplers Select and use appropriate personal protective equipment (gloves, masks, protective clothing, etc.) Wash/sanitize hands before and after sampling (in contact with specimens). Professionally trained/trained in sampling skills. Follow the prescribed procedure for taking samples. Clean and dispose of tools properly. 3.2 Ensure the safety of the person being sampled Use a disposable sampler. Sterilize instruments prior to specimen collection. Pre-sanitize tools with alcohol. Sampling in a separate, private, clean area. 3.3 Safety for medical staff Pack, store and transport patient samples appropriately.

3.4 Safety of People Around (Community) Collect and dispose of laboratory waste in an appropriate manner. Appropriate decontamination. Handle spills (if any) properly. There are many factors that will affect the test results obtained. However, the way samples are collected, stored and transported are the three most important factors that determine the quality of patient samples and have a major influence on the diagnostic results.