CCL18 and nasopharyngeal carcinoma: We observed the same NP-C detection rate (5/118; 4.2%) using the criteria of study Period 1 (i.e., NPC1 and NPC2 sequencing in all cases of suspected NP-C) as we did using the criteria of study Period 2 [i.e., NPC1 and NPC2 sequencing only when the ChT activity and/or CCL18/PARC concentration were elevated and/or NP-C SI was ≥70; 5/118 cases (4.2%)].