Olfactory Training for Postviral Olfactory Dysfunction: Systematic Review and Meta-analysis.

Area of Science:

• Otolaryngology
• Neurology
• Evidence-based Medicine

Background:

• Olfactory dysfunction is a common sequela of upper respiratory infections.
• Postviral olfactory dysfunction (PVOD) presents significant clinical challenges due to its prolonged nature.
• Olfactory training (OT) shows promise for general olfactory dysfunction but requires specific evaluation for PVOD.

Purpose of the Study:

• To evaluate the efficacy of olfactory training (OT) as a treatment for postviral olfactory dysfunction (PVOD).
• To conduct a pooled analysis of existing evidence to determine the effectiveness of OT for PVOD.

Main Methods:

• Systematic literature search of PubMed, Embase, and Web of Science databases following PRISMA guidelines.
• Inclusion of studies assessing OT efficacy for PVOD, excluding other olfactory loss causes or pharmacologic treatments.
• Meta-analysis of data from 16 full-text articles, focusing on Sniffin' Sticks olfactory testing (TDI scores).

Main Results:

• All included studies reported clinically significant improvements (TDI score increase >5.5) following OT.
• Meta-analysis revealed a 2.77-fold higher odds (95% CI, 1.67-4.58) of achieving clinically important TDI score differences in patients receiving OT compared to controls.
• Significant heterogeneity was observed in OT protocols used across studies.

Conclusions:

• Meta-analysis supports olfactory training (OT) as an effective treatment for postviral olfactory dysfunction (PVOD).
• Optimization of OT protocols may further enhance treatment outcomes.
• Current evidence supports the use of OT for both existing and emerging cases of PVOD.