Remote testing for PROP taster status assessment using solutions and paper disks

Solutions and paper disks are widely used methods for classifying people by their ability to perceive 6-n-propylthiouracil (PROP). Recently, remote sensory testing carried out under the supervision of the panel leader, has been found to be a valid alternative to the traditional lab-setting, offering several practical advantages. This study aimed to validate a protocol for PROP status assessment in remote condition and to compare the results obtained using solutions and paper disks. Individual differences in bitterness responsiveness and the relative classification between two different testing conditions (remote and laboratory) and two stimuli (solutions and disks) were compared. 77 subjects (18–30 years; 60 % women) participated in two sessions (one in laboratory and one in remote setting) and rated the perceived intensity of PROP solutions and disks. Mean PROP ratings did not vary across remote and lab conditions (p = 0.844). PROP phenotype classifications in remote-solution and lab-disk conditions were comparable to lab-solution reference condition (with a misclassification rate of 27 % and 31 % respectively, all occurring within contiguous groups). In contrast, the classification in remote-disk condition was not fully comparable (misclassification in respect to lab-solution of 48 % in contiguous groups, and 1.3 % in non-contiguous groups). One-solution test appears as a reliable procedure for PROP status assessment in live remote testing. Also, impregnated paper disks represent a suitable alternative to solution testing in conventional lab setting for practical reasons. However, paper disks could represent a valid option for data collection outside the lab, but they require rigorous in-person control by the sensory personnel when used.