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 applications, with specific contraindications in patients with active hematologic malignancies or post-allogeneic hematopoietic stem cell transplant. 1

Primary 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, creating risk of DNA contamination 1
• For patients with active hematologic malignancies, saliva or buccal swab samples are NOT recommended, since DNA is primarily extracted from leukocytes containing dysplastic cells 1
• In these high-risk populations, obtain skin biopsy at the time of bone marrow biopsy or other surgical procedure for germline testing instead 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 scraping can be used for sex determination through Barr body analysis, with non-overlapping ranges between males (0-4% Barr-body-positive cells) and females (20-78% Barr-body-positive cells) 2
• For oral microbiome studies, buccal swabs represent a specific intra-oral niche with advantages including ease of sampling, self-sampling capability, and repeated sampling feasibility 1
• The method has been validated for studying systemic effects of thermal injury on gene expression, demonstrating upregulation of nicotinic acetylcholine receptor subunits in burn patients 3

Standard Procedure Technique

Personal Protective Equipment

• Wear gloves for all patient interactions and procedures 4
• Use additional PPE (protective eyewear, mask, and gown) when spattering of blood or other body fluids is likely 4

Collection Method

• Use a soft sterile brush (bronchial brush) or small disposable plastic cup (Rhinoprobe) in the middle or inferior meatus 4
• Nasal scraping with Rhinoprobe is more comfortable for the patient and more accurate than swabbing 4
• For buccal mucosal scrapings, use a blunt sterile spatula to collect cells from the inner cheek 3, 2
• Place collected material in tubes containing appropriate growth medium or sterile containers 4

Sample Processing

• The material can be dislodged by oscillation and centrifuged at 400 g for 10 minutes 4
• For genetic analysis, cells can be stained (e.g., Papanicolaou staining for Barr body analysis) and observed under microscopy 2
• For molecular studies, samples can be processed using real-time reverse transcriptase polymerase chain reaction 3

Infection Control Precautions

Specimen Handling

• Place biopsy specimens in a sturdy, leakproof container labeled with the biohazard symbol during transport 4, 5
• If a specimen container is visibly contaminated, clean and disinfect the outside or place it in an impervious bag labeled with the biohazard symbol 4, 5

Equipment Sterilization

• Clean and heat-sterilize heat-tolerant devices between patients 4
• At minimum, high-level disinfect semicritical heat-sensitive devices according to manufacturer's instructions 4
• Use single-use devices for one patient only and dispose of appropriately 4

Medication Administration Safety

• Do not administer medication from a syringe to multiple patients, even if the needle is changed 4, 5
• Use single-dose vials for parenteral medications when possible 4, 5
• Cleanse the access diaphragm with 70% alcohol before inserting a device into multidose vials 4, 5

Critical Contraindications and Limitations

Patient-Specific 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

Technical Limitations

• Buccal swabs have low bacterial diversity and high human DNA proportion, which may limit microbiome studies 1
• Potential contamination from other oral surfaces can affect sample quality 1
• For patients with suspected primary ciliary dyskinesia, specimens can be used to measure ciliary beat frequency or perform electron microscopy, though electron microscopy is not 100% sensitive or specific 4

Common Pitfalls to Avoid

• Failure to recognize contraindications in hematologic malignancy patients leads to inaccurate genetic testing results 1
• Inadequate infection control practices can lead to cross-contamination between patients 4, 5
• Using buccal samples in post-transplant patients without considering donor cell chimerism results in false genetic results 1
• Insufficient sample collection or improper handling compromises diagnostic accuracy 4