Threshold and suprathreshold component analysis in olfactory dysfunction: a retrospective study.

Objective: To analyse variations in the n-butanol threshold and odour identification scores of the Connecticut Chemosensory Clinical Research Centre test in various grades of olfactory dysfunction and in different nasal conditions leading to olfactory loss.

Method: Retrospective observational study.

Results: All grades of olfactory dysfunction were predominantly noted among males. In chronic rhinosinusitis, anosmia or severe hyposmia was seen in 87.5 per cent of patients without polyps in comparison with 68 per cent of patients with polyps. In addition, 90 per cent of patients with atrophic rhinitis and post-traumatic loss had anosmia, but only 30.7 per cent of patients with allergic rhinitis had anosmia. Pepper was the most affected smell for all the nasal diseases except atrophic rhinitis, in which asafoetida and baby powder smells were affected more.

Conclusion: In most inflammatory sinonasal conditions, odour identification is relatively preserved even when the threshold is maximally affected. In patients with comparable olfactory dysfunction based on the Connecticut Chemosensory Clinical Research Centre test score, a relatively preserved suprathreshold odour identification score may predict better prognosis.