Investigating the Effect of Tumour Necrosis Factor Antagonist on Olfaction

Tumour Necrosis factor antagonists is a potent anti-inflammatory medication and has shown to improve olfactory function in murine models. The primary aim was to determine the effect of TNF antagonists on olfactory performance in humans. Secondary aim is to generate pilot data on the suitability of TNF for a randomised controlled trial in patients with smell disorders.

This study is a single centre observatory prospective proof of concept cohort study. Adult patients are recruited from a tertiary rheumatology centre, who are to be initiated on TNF antagonists therapy (adalimumab biosimilar) for the first time. Participants were assessed with a simple questionnaire and a baseline olfactory assessment with the extended Sniffin' Stick Test. Participants were then brought back after 3 months of treatment for a repeat questionnaire and Sniffin' Sticks Test.

The primary outcome was to determine the difference between smell test scores in the Sniffin' Sticks TDI score before and after 3-months of treatment. Secondary outcomes include changes in visual analogue score from baseline to follow-up (questionnaire).

Sixty-three participants were recruited in the study; 21 were lost to follow up and two had stopped taking their medication, hence 40 were included in the analysis. There was no statistically significant improvement in TDI score of all participants at 3 months after treatment (p value = 0.08). However, analysis of participants who had olfactory dysfunction at baseline (n = 20, TDI < 31 or 30.5 if aged 20-30) showed a statistically significant improvement in TDI score after 3 months (p value = 0.012).

TNF antagonists have the potential to improve olfactory function in those with olfactory dysfunction and should be subjected to further study in a selected group of patients with olfactory dysfunction.