The participant has signs or symptoms suggestive of nasopharyngeal carcinoma, or has a condition that needs to be differentiated from nasopharyngeal carcinoma

Detect VCA-IgA, EBNA1-IgA, and EBV-DNA for all participants.

Measure the sensitivity of Epstein-Barr Virus (EBV) C Promoter Methylation as a diagnostic marker for Nasopharyngeal Carcinoma (NPC). Sensitivity will be calculated as the proportion of true positive cases (patients correctly identified with NPC) out of the total number of actual NPC cases.

Measure the specificity of Epstein-Barr Virus (EBV) C Promoter Methylation as a diagnostic marker for Nasopharyngeal Carcinoma (NPC). Specificity will be calculated as the proportion of true negative cases (patients correctly identified without NPC) out of the total number of actual non-NPC cases.

Evaluate the agreement between Epstein-Barr Virus (EBV) C Promoter Methylation and the gold standard diagnostic methods for Nasopharyngeal Carcinoma (NPC) using the Kappa statistic. The Kappa value will indicate the consistency and reliability of EBV C Promoter Methylation as a diagnostic tool compared to established diagnostic criteria.

This measure evaluates the positive, negative, and total concordance rates, as well as the Kappa Value, between test reagents and two established sequencing techniques-Sanger sequencing and pyrosequencing-for detecting Epstein-Barr virus C promoter methylation. The accuracy of these detection methods is assessed by comparing their results to those obtained through the widely used and mature technologies of Sanger dideoxy chain termination and pyrosequencing, often considered the "gold standards" for gene sequence analysis. This study aims to evaluate the reliability and accuracy of the test reagents in identifying methylation of the EBV C promoter, using these established sequencing benchmarks.

This outcome measures the agreement rates between EBV C promoter methylation and EBV-related antibodies in the diagnosis of nasopharyngeal carcinoma without a gold standard for comparison. It includes an evaluation of the positive concordance rates, negative concordance rates, and Kappa value, which might reflect limited conclusiveness but offer insight into the relative alignment of these diagnostic tests. This will help ascertain their comparative reliability and diagnostic utility in a real-world setting.

During follow-up consultations 1 to 6 months post-discharge, nasopharyngeal swabs will be collected to observe the dynamics of EBV C promoter methylation before and after treatment for nasopharyngeal carcinoma