OBJECTIVE Olfactory dysfunction is a common problem that is most frequently attributed to upper respiratory infection . Postviral olfactory dysfunction (PVOD) can be prolonged and clinically challenging to treat . Olfactory training (OT) has demonstrated potential benefit for patients with nonspecific olfactory dysfunction . We sought to evaluate the efficacy of OT specifically for PVOD by pooled analysis of the existing evidence .
DATA SOURCES PubMed, Embase, and Web of Science .
REVIEW METHODS Following PRISMA guidelines, PubMed, Embase, and Web of Science databases were queried and abstracts screened independently by 2 investigators . We included studies evaluating the efficacy of OT for PVOD and excluded studies evaluating pharmacologic interventions or olfactory loss from other causes .
RESULTS Of the initial 1981 abstracts reviewed , 16 full-text articles were included . Sniffin' Sticks olfactory testing results were reported in 15 (93 %) studies as threshold (T), discrimination (D), and identification (I) subscores and TDI total scores . All studies reported clinically significant results after OT, defined as a score improvement of TDI> 5.5 . Four studies were included in the meta-analysis, in which pooled estimates revealed that patients with PVOD who received OT had a 2.77 (95% confidence interval , 1.67-4.58) higher odds of achieving a clinically important difference in TDI scores compared to controls .
CONCLUSION Meta-analysis of existing data demonstrates clinically significant improvements in PVOD associated with OT . Variability exists among OT protocols and may benefit from further optimization . Existing data supports the use of OT for the treatment of existing and newly emerging cases of PVOD.