At least 4 levels of the nasopharyngeal tissues should be examined, one of which should include the nasopharyngeal duct, (5, 6, 7, 8, 9) to allow adequate examination of the squamous, transitional (non-ciliated respiratory), respiratory (ciliated respiratory) and olfactory epithelium, and the draining lymphatic tissue (NALT; 10, 11).
Tuleks uurida vähemalt nelja nasofarüngeaalsete kudede tasandit, millest üks peaks hõlmama nasofarüngeaalset kanalit (5, 6, 7, 8, 9), et võimaldada asjakohaselt uurida skvamoosrakulist, ülemineku- (hingamisteede clara-rakud), hingamisteede (ripsepiteel) ja olfaktoorset epiteeli ning neid dreenivat lümfikude (NALT; 10, 11).