Evaluation of nasal and nasopharyngeal swab collection for the detection of Epstein-Barr virus in nasopharyngeal carcinoma.

Epstein-Barr virus detection using nasopharyngeal swabs has been suggested as a potential screening test that could improve the specificity of current EBV-based serological assays. However, application requires insertion of the swab deep into the nasopharynx, a procedure not amenable to non-clinic screening. We reasoned that swabbing the more easily accessible nasal cavity might provide an appealing alternative for NPC detection. Patients > 18 years of age diagnosed with histologically confirmed NPC were recruited from the Otolaryngology Department at the National Taiwan University Hospital. ENT clinicians collected both nasal and nasopharyngeal swabs. EBV DNA and cellular beta-globulin DNA were quantified using quantitative PCR targeting a highly-conserved region of the BKRF1 gene. EBV DNA was detectable (non-zero) in all 34 nasopharyngeal swabs and above the positivity threshold of 1666 EBV copies in 30 (88.2%) patients. EBV DNA was detectable in 50% of 34 nasal swabs and above the positivity threshold in four (11.8%) patients. Average EBV DNA levels were >3-fold higher (P < 0.001) in nasopharyngeal compared to nasal swabs. Among the 17 NPC patients with detectable EBV DNA in both swab types, we observed correlation (P < 0.01) between EBV DNA measurements. Our data represent the first evaluation of EBV DNA collected from nasal swabs. Given current EBV DNA amplification techniques, nasopharyngeal swabs remain more sensitive than nasal swabs for NPC detection.