Screening nasopharyngeal carcinoma by detection of the latent membrane protein 1 (LMP-1) gene with nasopharyngeal swabs

BACKGROUND: Nasopharyngeal carcinoma (NPC) is a common head and neck cancer in Taiwan. The goals of the current study were to investigate whether a nasopharyngeal swab technique could provide enough DNA for polymerase chain reaction (PCR) analysis of the Epstein-Barr virus (EBV)-derived latent membrane protein 1 (LMP-1) gene and to determine the feasibility and reliability of diagnosing NPC by detection of LMP-1 in the nasopharynx. METHODS: 320 adults underwent nasopharyngoscopy and nasopharyngeal swab to obtain cells for the LMP-1 PCR assay; some patients also underwent nasopharyngeal biopsy. RESULTS: An amount of DNA that was sufficient for PCR was extracted from 96.3% of the swab samples. By detecting LMP-1 in nasopharyngeal swabs, NPC was diagnosed with a false positive rate of 12.7% (7 of 55 patients), a false negative rate of 1.6% (4 of 253 patients), sensitivity of 87.3% (48 of 55 patients), specificity of 98.4% (249 of 253 patients), a positive predictive value of 92.3% (48 of 52 patients), and a negative predictive value of 97.3% (249/256 patients). NPC was diagnosed by nasopharyngoscopy with a false positive rate of 38% (30 of 79 patients), a false negative rate of 0.4% (1 of 241 patients), sensitivity of 62% (49 of 79 patients), specificity of 99.6% (240 of 241 patients), a positive predictive value of 98% (49 of 50 patients), and a negative predictive value of 88.9% (240 of 270 patients). Only 7 (0.2%) of 256 patients with a diagnosis other than NPC had LMP-1 detected in the nasopharyngeal space. CONCLUSIONS: Detecting EBV genomic LMP-1 by nasopharyngeal swab diagnosed NPC with 87.3% sensitivity and 98.4% specificity. EBV genomic DNA usually is not detected by PCR-based methods in the nasopharyngeal space. Its incidence is estimated to be as low as 0.2% among the general population. The nasopharyngeal swab coupled with PCR-based EBV LMP-1 detection could serve as part of a screening program for high-risk populations.