These measures examine different aspects of smell function. Threshold testing addresses the minimum odor strength a person can detect, discrimination assesses whether different odors can be distinguished, and identification evaluates whether an odor can be recognized or named. Comparing these results helps characterize the pattern of impairment rather than reducing olfactory performance to a single overall score.
Testing each nostril separately allows clinicians to compare olfactory performance between the two nasal passages. This side-specific approach can reveal whether smell function is similarly reduced bilaterally or differs from one side to the other. Such comparisons add clinical detail when interpreting odor threshold, discrimination, and identification results.
Results may help distinguish a conductive problem, in which odor access is affected, from neural or central dysfunction involving the olfactory nerve or related brain pathways. The distinction depends on the pattern across testing measures and clinical context, so olfactory findings contribute to evaluation rather than independently establishing a specific cause.
Olfactory impairment does not always appear as reduced sensitivity. Some patients experience distorted perception, meaning an odor may be sensed but experienced inaccurately or differently from expected. Recognizing this pattern is clinically important because testing can characterize changes in the quality of smell as well as reduced ability to detect, distinguish, or identify odors.
A clinician presents standardized odorants under controlled conditions, commonly assessing one nostril at a time. The patient’s responses are used to evaluate odor threshold, discrimination, and identification. Recording these distinct outcomes provides a structured profile of olfactory function and supports comparison with the patient’s symptoms and relevant clinical history.
Clinicians may use the assessment when evaluating smell changes after head injury or respiratory infection, and when investigating possible neurodegenerative disease or other disorders. Repeated testing can also provide an objective measure for monitoring recovery or progression, helping show whether olfactory function changes over time rather than relying only on subjective reports.