2.3 Test procedure
Sniffin’ Sticks Olfactory Identification test: The test comprises 16
felt-tip pen-like d-evices; only one olfactory pen cap can be opened at
a time. The pen tip was placed appr-oximately 2 cm under the middle of
the subject’s double nostrils and did not touch the su-bject’s skin. The
time for the subject to smell each pen shall not exceed 2–3 seconds,
with an interval of about 30 seconds. After presenting a stick, the
subject was provided with f-our odor descriptors to select the option
that could best describe the presented odor. Even if subjects were
uncertain about the odor, they were required to use the exclusion method
to make a choice. The test was repeated successively until all 16 odors
were presented.