When is buccal (bucal) scraping medically indicated?

When to Perform Buccal Scraping

Buccal scraping is medically indicated in three primary scenarios: (1) for genetic testing when blood samples cannot be used due to hematologic malignancy or post-transplant status, (2) for diagnosing mucocutaneous fungal infections, and (3) for sex determination in forensic or diagnostic contexts.

Genetic Testing Indications

Post-Hematopoietic Stem Cell Transplant Patients

• Buccal cells should NOT be 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
• Fibroblast culture from skin biopsy is the preferred alternative when blood testing is contraindicated 1
• If fibroblast culture is unavailable, buccal swabs may be considered with full awareness of the contamination risk 1

Active Hematologic Malignancies

• Saliva or buccal swab samples are NOT recommended for patients with active hematologic malignancies, as DNA from these samples is primarily extracted from leukocytes containing dysplastic cells 1
• Obtain skin biopsy at the time of bone marrow biopsy or other surgical procedure for germline testing 1
• For patients in remission from myeloid malignancies, blood samples can be used, though some clinicians prefer skin biopsy for all myeloid cases 1

Infectious Disease Diagnosis

Mucocutaneous Fungal Infections

• 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
• This is a Grade B-III recommendation from the Infectious Diseases Society of America 1

Herpes Simplex or Herpes Zoster

• Skin scrapings may be examined for the presence of giant cells when herpes infection is suspected 1

Forensic and Diagnostic Applications

Sex Determination

• Buccal scraping can determine sex through Barr body analysis, showing 39.29% Barr-body-positive cells in women versus 1.14% in men with non-overlapping ranges 2
• This method is simple, accurate, and economical for forensic investigations 2

Critical Timing Considerations for Breast-Fed Infants

• Wait at least 60 minutes after breast feeding before collecting buccal smears to avoid maternal cell contamination 3
• Thoroughly clean the buccal mucosa with a cotton swab applicator prior to sample collection 3
• Maternal cells are present in 47.9% of samples collected within 5 minutes of feeding, dropping to only 6.9% at ≥60 minutes 3

Oral Microbiome Research (Not Routine Clinical Care)

• Buccal swabs represent a specific intra-oral niche for microbiome studies 1
• Advantages include ease of sampling, self-sampling capability, and repeated sampling feasibility 1
• Disadvantages include low bacterial diversity, high human DNA proportion, and potential contamination from other oral surfaces 1

Important Caveats

Quality Concerns

• DNA degradation significantly affects total yield and performance of buccal DNA compared to blood DNA in microarray-based genotyping 4
• Genotyping results can be seriously compromised without careful quality and yield assessment 4
• Buccal DNA quality is sufficient for PCR-based assays but may not perform as reliably as blood for more demanding applications 4, 5

When NOT to Use Buccal Scraping

• Active hematologic malignancies requiring germline testing 1
• Post-allogeneic HSCT patients (use fibroblasts instead) 1
• When high-quality DNA is critical for complex genetic analyses 4
• Breast-fed infants within 60 minutes of feeding 3