Olfactory function assessment
Both the olfactory threshold and the odor discriminative ability were assessed. All tests were conducted in a quiet room, by the same operators. Olfactory function assessment was carried out by means of the Connecticut Chemosensory Clinical Research Center orthonasal olfaction test (CCCRC) [7-11]. The CCCRC is a simple, validated and widely used test, that includes a butanol threshold assessment and an odor identification test using common odors.
Threshold testing was performed presenting solutions of N-bunatol in deionized waters, decreasing concentration in 8 steps. The strongest butanol concentration was 4% in 60 mL of deionized water (bottle 0). Each other bottle (from 1 to 8) contained a subsequent 1:3 N-butanol dilution. Two identical squeezable bottles were presented to the patient: one containing the N-butanol solution, Starting from the major dilution, and the other filled with deionized water. The patient was then asked to close one nostril and squeeze the bottle immediately below the other, reporting which of the two bottles smelled most. The threshold was identified when the subject gave the correct answer 4 times. In case of error, the next most concentrated solution was given to the patient. The threshold was quantified for each of the two nostrils with a score from 0 to 8 corresponding to less concentrated bottle that the patient was able to correctly detect. The average between values of the two nostrils expressed the overall score.
For the identification test, common odorants, familiar to the Italian population [Table 1], were placed inside 180 mL opaque jars covered with gauze. One at a time, the samples were presented to the patient in the same way as the threshold test. Therefore, the patient was asked to identify the odorant on a list containing the 10 test items and 10 distractors [Table 1]. Score ranged from 0 to 10 and was obtained from the average of the two nostrils.
The threshold and identification test scores, after being analyzed separately, were finally converted into the CCCRC composite score. The scoring system is shown in table 2 [Table 2].