What are the guidelines and precautions for a buccal (bucal) scraping procedure?

Buccal Scraping: Guidelines and Precautions

Buccal scraping is a minimally invasive procedure for collecting epithelial cells from the inner cheek, primarily used for genetic testing, infectious disease diagnosis, and research purposes, with specific contraindications in patients with active hematologic malignancies or post-allogeneic hematopoietic stem cell transplant. 1

Clinical Indications

Genetic Testing Applications

• Buccal cells should NOT be used as the first choice for genetic testing in allogeneic HSCT recipients, as donor-derived cells progressively replace the patient's buccal epithelial cells over time, risking DNA contamination 1
• For patients with active hematologic malignancies, saliva or buccal swab samples are NOT recommended, as DNA is primarily extracted from leukocytes containing dysplastic cells 1
• In these populations, skin biopsy obtained at the time of bone marrow biopsy or other surgical procedure should be used instead for germline testing 1

Infectious Disease Diagnosis

• Perform scraping for potassium hydroxide 10% preparation to verify the presence of yeast or dermatophytes when mucocutaneous fungal infection is suspected 1
• If mucocutaneous candidiasis is refractory to empirical treatment, culture the scraping to detect drug-resistant species 1

Research and Forensic Applications

• Buccal swabs represent a specific intra-oral niche for microbiome studies, with advantages including ease of sampling, self-sampling capability, and repeated sampling feasibility 1
• Sex determination through Barr body analysis can be performed using buccal scrapings, with non-overlapping ranges for men (0-4% Barr-body-positive cells) and women (20-78% Barr-body-positive cells) 2

Procedural Technique

Collection Methods

• Use a soft sterile brush (bronchial brush) or small disposable plastic cup (Rhinoprobe) in the middle or inferior meatus for cell collection 3
• The Rhinoprobe method is more comfortable for the patient and more accurate than swabbing 3
• For nasal applications, 2-10mL of 0.9% sodium chloride at body temperature can be instilled with a syringe, with the patient refraining from swallowing for approximately 10 seconds before collection 3

Infection Control Precautions

• Wear gloves for all patient interactions and procedures 3, 4
• Use additional PPE (protective eyewear, mask, and gown) when spattering of blood or other body fluids is likely 3, 4
• For oral surgical procedures, perform surgical hand antisepsis using an antimicrobial product before donning sterile surgeon's gloves 3, 4

Specimen Handling

• Place specimens in a sturdy, leakproof container labeled with the biohazard symbol during transport 3, 4
• If the specimen container is visibly contaminated, clean and disinfect the outside or place it in an impervious bag labeled with the biohazard symbol 3, 4
• For genetic testing, the material should be dislodged by oscillation and centrifuged at 400g for 10 minutes 3

Important Limitations and Caveats

Sample Quality Considerations

• Disadvantages of buccal swabs include low bacterial diversity, high human DNA proportion, and potential contamination from other oral surfaces 1
• Thermal injury may cause systemic upregulation of nicotinic acetylcholine receptor genes in buccal mucosa, potentially affecting gene expression studies 5
• Smoking induces significant morphological changes in buccal epithelial cells, including decreased nuclear and cell perimeter, which may affect sample interpretation 6

Contraindications

• Active hematologic malignancies requiring germline testing should NOT use buccal scraping 1
• Post-allogeneic HSCT patients should use fibroblasts instead of buccal scraping for genetic testing 1

Common Pitfalls to Avoid

• Failure to recognize that buccal cells in HSCT recipients become progressively replaced by donor cells, leading to inaccurate genetic testing results 1
• Using buccal samples for genetic testing in patients with active hematologic malignancies, where circulating dysplastic cells contaminate the sample 1
• Inadequate infection control practices during collection, which can lead to cross-contamination 3, 4
• Failing to properly label specimens with biohazard symbols, creating safety risks during transport and processing 3, 4