Biological Sample Collection Notes

The collection of biological samples is a fundamental procedure in clinical diagnosis and disease monitoring.
A correctly taken and
handled sample ensures the reliability of laboratory results.
This manual is aimed at healthcare personnel in charge of sample collection, with emphasis on specific procedures and biosafety standards.

Objective: To obtain a venous blood sample when other veins are inaccessible.
Materials:
- Gloves
- 70% alcohol swabs
- Hypodermic needle or butterfly needle
- Collection tubes (Vacutainer)
- Bandage
Procedure:
1. Wash hands and put on gloves.
2. Review and select a visible and palpable dorsal vein.
3. Present the material.
4. Disinfect the area.
5. Apply a tourniquet to the wrist.
6. Prepare the needle with the tube.
7. Insert the needle with the bevel up at an angle of 10 to 15 degrees.
8. Extract the necessary blood.
9. Release the tourniquet.
10. Remove the needle and apply pressure with a dry swab.
11. Discard the needle, put on the cap, and mix if necessary.
12. Once the area has healed, apply the bandage.
Precautions:
- Avoid puncturing multiple times.
- Do not apply excessive pressure post-extraction.

Objective: To detect infectious agents in the pharynx (mainly bacteria and viruses).
Materials:
- Sterile swab with transport medium
- Gloves and mask
- Tongue depressor
Procedure:
1. Explain the procedure to the patient.
2. With the patient seated, tilt the head back slightly.
3. Assemble the material for extraction: two swabs on one hand and a tongue depressor on the other.
4. Use a tongue depressor to visualize the tonsils and pharyngeal wall.
5. Ask the patient to say and maintain the vowel "A" for a better view of the pharynx.
6. Insert the swabs without touching saliva, tongue, or gums.
7. Take the sample by gently rotating over the pharynx, making circular movements for better collection.
8. Remove the swabs without touching again.
9. Inoculate in the culture medium or in the transport tube.
Precautions:
- Do not take the sample after eating.
- Avoid contamination of the swab.
- Perform the collection in a place with a sterile, clean field, avoiding drafts.

Objective: To take a sample of urethral secretion to diagnose sexually transmitted infections (STIs).
Materials:
- Gloves, goggles, and gown
- Sterile swab
- Culture medium or transport medium
- Tongue depressor
Procedure (in men):
1. Inform and obtain patient consent regarding the procedure to be performed.
2. Ask the patient to retract the foreskin if necessary, using the tongue depressor to improve the maneuver.
3. Carefully insert the swab 2-4 cm into the urethra.
4. Rotate gently for 2-3 seconds.
5. Remove the swab and insert it into the transport medium or inoculate it into the culture medium.
Precautions:
- Take the sample at least 2 hours after the last urination.

Objective: To take a sample of vaginal secretion for the detection of microorganisms responsible for vaginal infections.
Materials:
- Sterile speculum
- Gloves
- Flashlight (optional)
- 2 sterile swabs
- Culture media
Procedure:
1. Explain the procedure and ensure privacy.
2. Ask the patient to be placed in a gynecological position.
3. Place the 2 swabs in the right hand and the previously lightly lubricated speculum or vaginal mirror in the other hand for sampling.
4. Insert the speculum into the vaginal opening, turning it at the same time as it is opened.
5. Locate secretions.
6. Take the sample with swabs from the cervix and vaginal walls.
7. Remove the swabs first, then the vaginal mirror.
8. Inoculate in the culture media or transfer the swabs to the transport medium.
Precautions:
- Ensure aseptic conditions.
- Avoid cross-contamination between sites.
- Do not have consumed antibiotics in the last 72 hours.
- Do not have consumed food or beverages in the last 8 hours (except water).

Objective: To take a sample to identify fungi on skin, nails, or hair.
Materials:
- Sterile scalpel or curette
- Slides and Petri dishes
- Gloves
Procedure:
1. Clean the area with alcohol.
2. Take or scrape scales of skin, nail fragments, or affected hairs.
3. Deposit in a sterile container or slide.
4. Label and send to the laboratory for culture analysis.
Precautions:
- Do not apply antifungal creams before collection.

Objective: To prepare media to be inoculated and study the growth of microorganisms.
Materials:
- Dehydrated medium powder (e.g., Blood Agar, Sabouraud, McConkey)
- Distilled water
- Flasks
- Autoclave
- Beaker
- Bunsen burner
- Petri dishes
Procedure:
1. Weigh the Erlenmeyer flask.
2. According to the manufacturer's instructions, weigh the agar according to what is going to be prepared.
3. Dissolve in the beaker with distilled water according to the amount of medium that is going to be prepared.
4. With the help of the Fisher burner, heat until completely dissolved. Taking care of boiling or overheating to avoid accidents.
5. Place cap and hood.
6. Sterilize in an autoclave at 121°C for 15 minutes with 15 pounds of pressure.
7. Pour into sterile Petri dishes and let solidify.
Precautions:
- Sterilize correctly.
- Label with preparation date and type of medium.

Manual de procedimientos para toma de muestras. Instituto Nacional de Salud.
WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. World Health Organization.
Manual de Microbiología Médica. Patrick R. Murray.
Normas Oficiales Mexicanas para el Diagnóstico de Enfermedades Transmisibles.
Toma y manejo de muestras biológicas. Ministerio de Salud de Colombia.