The Ultimate Guide to Medical Specimen Collection and Transport
1. Blood Specimens
When collecting blood for culture, extra caution is needed. Many microorganisms, especially staphylococci and Propionibacterium, typically found on or near the skin surface, can easily contaminate the specimen.
To collect a blood specimen, follow these steps for venipuncture:
(1) First, clean the skin at the venipuncture site with 70% alcohol (prepared with sterile distilled water).
(2) Then, swab with tincture of iodine. For those allergic to iodine, use 70% alcohol again, ensuring to swab from the center outward.
(3) Temporarily cover the area with cotton soaked in 70% alcohol.
(4) Apply a tourniquet to the upper arm, not too tight, and ask the patient to repeatedly open and close their fist.
(5) Remove the cotton, use a 20 or 21 gauge needle with a 10ml syringe to draw 10ml of blood. For infants or children, draw only 1-5ml.
(6) Directly inoculate the specimen into appropriate culture media [such as tryptic soy broth and thioglycollate medium or standard blood culture bottles].
2. Urine Specimens
Urine specimens are usually collected using the clean-voided method. Before collection, the urethral opening should be cleaned with soap and water (patient education is necessary; currently, most major hospitals do not emphasize this requirement for urine collection). Discard the first part of the urine stream, collecting the mid-stream or near-end stream in a sterile container. Catheterization for urine collection (especially for female patients) should be avoided unless necessary, as it can lead to urinary tract infections. The collection method must be noted on the lab form, along with any recent antibiotic treatment. These two points should be included on the test requisition form. If the specimen cannot be transported or cultured immediately after collection, it should be refrigerated (4-8°C) for no more than 6 hours. Urine specimens are not used for gonorrhea testing.
3. Genital Tract Specimens
Genital tract specimens should be collected using two sterile swabs, taken separately, for direct smear preparation. For menstruating or adult women, smears should be taken from the urethra, cervix, or rectum (if gonococcal infection is suspected). For young girls suspected of having gonococcal vulvovaginitis, specimens should be taken from the outer vaginal area. For men suspected of acute gonorrhea, specimens should be taken from the urethra for smear and culture. For suspected chronic gonorrhea, specimens may be taken from the prostate or seminal vesicles by a physician.
Swab specimens can be directly inoculated onto appropriate media [such as chocolate agar and modified Thayer-Martin agar], or placed in special transport media/devices (containing CO2 and modified Thayer-Martin agar). Refrigerated isolation or transport media should be brought to room temperature or 35°C for about half an hour before use, as Neisseria gonorrhoeae is temperature-sensitive. Chocolate agar should contain IsoVitaleX or supplement B to increase isolation rates. For prenatal Group B Streptococcus (GBS) screening at 35-37 weeks of pregnancy, genital swabs can be directly placed in GBS selective broth or LIM selective enrichment broth to increase GBS isolation rates.
4. Cerebrospinal Fluid (CSF) Specimens
CSF is usually obtained through lumbar puncture, performed by a physician as follows: The lower back is disinfected with 70% alcohol or 2% iodine tincture (as with blood specimen collection) and anesthetized. A special stylet needle is then gently inserted between the third and fourth lumbar vertebrae along the midline into the spinal subarachnoid space. The entire process must be conducted under the strictest aseptic conditions. For infants or children, position the head and hands on folded sheets or blankets, or place the head on the abdomen to facilitate lumbar puncture. Distribute the CSF into 3 small sterile tubes [using a Sterile 3-tube Set for CSF is convenient]. Then quickly send the third (or first) tube to the microbiology laboratory.
5. Fecal Specimens and Rectal Swab Specimens
For microbial examination, feces can be directly placed in a sterile plastic container after defecation. Generally, the mucus-containing parts of the stool are most suitable for microbial examination.
To collect rectal specimens, clean the anal area with soap, water, and 70% alcohol. Then insert a swab moistened with sterile saline or liquid transport medium into the anus, rotate it to contact the rectal mucosa, then remove and place it in an Aerobic TransCult Swab transport device (for Salmonella) or a container with buffered glycerol saline transport medium (for Shigella), and immediately send to the laboratory. Sometimes, fecal specimens can also be obtained from gloves used during digital rectal examination.
For parasitological examination, fecal specimens in sterile plastic containers should be quickly sent to the laboratory for immediate examination of the still-warm stool. This is particularly important because some parasites like amoebas quickly lose motility as the stool cools. If immediate examination is not possible, the container can be placed in a water bath at about 37°C to maintain warmth for a certain period.
For microbial examination of fecal or rectal swab specimens, rapid transport and inoculation are crucial. Delays may allow overgrowth of non-pathogenic intestinal bacteria, making pathogen isolation difficult.
6. Pus or Wound Specimens
Pus from abscesses and boils can be obtained through drainage. First, clean the affected area with 70% alcohol, let it dry, then make an incision with a sterile blade and collect the specimen with a sterile swab. For extensive wounds, try to open the surface area and collect specimens from deeper layers to avoid contamination from surface microorganisms. After collection, swabs should be immediately placed in anaerobic specimen collection tubes/devices [Anaerobic TransCult Swab].
Pus or wound specimens often require anaerobic culture, so great care must be taken during collection to minimize exposure to air. It's best to aspirate specimens directly from the lesion with a syringe; if swabs must be used, place them in Anaerobic TransCult Swab medium, or insert the needle through a silicone stopper, or inject into an anaerobic specimen collection vial [Anaerobic vial], then quickly send to the laboratory for inoculation onto appropriate media.
7. Nasal and Throat Specimens
To collect nasal specimens for culture, use a sterile swab with a rigid plastic handle or a flocked swab [with a dense, brush-like tip] inserted directly into the nasal cavity. Avoid using large, loose cotton swabs that might slip or get stuck in the patient's nasal cavity. For throat specimens, collect under good lighting, using swabs to sample the actual lesion site. At least two swabs should be collected separately. After collection, place in appropriate anaerobic transport media to prevent drying or contamination.
When Corynebacterium diphtheriae infection is suspected, perform both throat and nasal-pharyngeal cultures to increase isolation rates. If diphtheria-like lesions are present in the throat, in addition to culture, direct smears should also be made, as the causative organisms of Vincent's angina, which can resemble diphtheria, can only be detected through smear examination.
8. Nasopharyngeal Specimens
The nasopharynx refers to the upper half of the throat behind the soft palate. To collect specimens from this area, use a thin, flexible-handled nasopharyngeal flocked swab. Insert it through the nasal cavity into the nasopharynx, gently rotate to swab, then withdraw. Repeat through the other nostril. After collection, place in the aforementioned Amies transport medium or Aerobic TransCult Swab and quickly send to the laboratory. Care must be taken to avoid saliva contamination during nasopharyngeal specimen collection.
9. Sputum Specimens
Generally, sputum specimen collection is most prone to errors: either too little is collected, or the specimen contains only oral, nasal, or throat secretions without actual sputum. Before collection, clean teeth with a toothbrush (or rinse mouth if difficult), then expel respiratory secretions. The collected sample must truly represent lung secretions. Usually, morning sputum is most abundant and most likely to contain pathogens such as Mycobacterium tuberculosis or Streptococcus pneumoniae. After deep coughing, sputum should be placed in a sterile plastic container with a tight-sealing lid or a sterile centrifuge tube to prevent self-infection or infection of others. For mycobacterial diagnosis, sputum specimens should be collected for 3 consecutive days, 3 times in total, to increase detection rates.
Children often swallow sputum into their stomachs, and adults may do so during sleep. To collect sputum from children or when satisfactory coughed sputum cannot be obtained from adults, gastric contents can be aspirated, preferably before eating or drinking in the morning. For microbial examination of bronchial secretions, specimens can be obtained using a bronchoscope.
10. Body Fluid Specimens
Body fluid specimens such as pleural fluid, peritoneal fluid, pericardial fluid, or synovial fluid are usually collected by physicians using aseptic technique. A trocar or specially designed needle is inserted into the collection site, and fluid is aspirated with a syringe. Since all fluids require anaerobic culture, collection and transport should avoid air contact. They can be directly inoculated into blood culture bottles and/or collected in anaerobic transport tubes.
11. Conjunctival Specimens
Conjunctival specimens can be collected using a swab moistened with sterile saline. Care must be taken to avoid spreading infection to adjacent eye areas. After collection, swabs should be placed in Amies transport medium or TransCult Swab to prevent drying. Note that the specimen should be labeled as from the left or right eye.
12. Specimens for Fungal Culture
To collect skin specimens, first clean the lesion area with 70% alcohol, then use a sterile blade or slide edge to scrape specimens from the lesion margins and place them in a sterile culture dish. Nail specimens are collected similarly, but it's necessary to scrape deeper into newly infected nail tissue. For hair or scalp scale specimens, a Wood's lamp (ultraviolet light) can be used to illuminate the affected area, as infected areas often fluoresce. Then, use sterile forceps to pluck hair or scalp scales and place them in a sterile culture dish.
Mantacc Swab Supply
Our flocked nasopharyngeal swab uses a medical-grade ABS shaft with a flocked tip design. The flocked swab is manufactured using spray and electrostatic charge methods, allowing millions of nylon fibers to adhere vertically and uniformly to the handle end. The capillary action between the nylon fibers facilitates sample collection and elution. Flocked swabs have far superior sample collection and release capabilities compared to traditional twisted swabs. They are thin, soft, and mainly used for nasopharyngeal sampling of respiratory diseases such as COVID-19, influenza A and B, respiratory syncytial virus, and mycoplasma pneumoniae.
