Evaluation of odor recognition threshold measurement methods in T&T olfactometry: A survey study

The odor recognition thresholds in T&T olfactometry are measured by either the examiner's judgment of the patients' odor expression for each standard odor or by the patient's choice of the correct response from an olfactory term table. This study aimed to clarify the correct odor expressions and use of the olfactory term table.

A questionnaire was administered to otolaryngologists or medical staff in charge of testing at facilities where T&T olfactometry is performed. The questionnaire consisted of the facility's background, environment and procedures of T&T olfactometry, choice of the correct answer with five different standard odors, and use of the olfactory term table. For the choices, the expressions used were those considered correct at Nippon Medical School Tama Nagayama Hospital and the Kyoto Nose and Allergy Clinic.

A total of 81 valid responses were obtained. Most respondents belonged to medical and educational institutions (59.3%, 48/81). The laboratories in the respondents' institutions were completely ventilated using various methods. Clinical laboratory technicians inspected 51.7% (45/81) of the facilities. The order of standard odors in the odor recognition threshold test differs depending on the facility. When the examiner was unsure about the answer given by the patient in the odor recognition threshold test, 16.1% (9/56) of the respondents chose "present the olfactory term table," 33.9% (19/56) chose "increase the concentration," and 37.5% (21/56) chose "present the olfactory term table" or "increase the concentration," depending on the situation. A total of 96.4% (54/56) of the facilities treated odor expressions other than those in the olfactory term table as correct, and the odor expressions that were considered correct differed from facility to facility. Of the respondents, 80.2% (65/81) answered "I know the olfactory term table," and the mean value of satisfaction with the current olfactory term table was 4.4 ± 3.0. Of the respondents, 81.5% (53/65) answered that "the timing of presenting the olfactory term table should be standardized in all facilities."

In the odor recognition threshold test by T&T olfactometry, this study revealed that the odor expressions considered as correct answers for the standard odors and the use of the olfactory term table differed among facilities.