The Effect of Traditional Chinese Medicine on Postviral Olfactory Dysfunction: A Systematic Review and Meta-Analysis

Objective. The aim of this study is to evaluate the efficacy and safety of traditional Chinese medicine (TCM) for postviral olfactory dysfunction (PVOD). Methods. PubMed, EMBASE, Cochrane Central Register of Controlled Trials, China Network Knowledge Infrastructure (CNKI), Chinese Scientific Journal Database (VIP), Chinese Biomedical and Medical (CBM) Database, and Wanfang Database were electronically searched from their inception to July 25, 2022. Two authors independently performed study selection, data extraction, and quality assessment to ensure systematic quality evaluation. Randomized controlled trials (RCTs) comparing TCM with olfactory training and/or drug therapy (OTDT) were included. The outcomes were the effective rate, QOD-P, TDI score, UPSIT score, and adverse effects. Cochrane RoB was the guideline used to evaluate the methodological quality of the included trials. RevMan 5.3 software was used for statistical analysis. Results. A total of 6 RCTs involving 467 patients with PVOD were selected. Compared with OTDT, TCM plus OTDT decreased QOD-P (MD = -1.73, 95% CI (-2.40, -1.06), P < 0.0001) but did not increase the effective rate (T & T) (RR = 1.28, 95% CI (0.86, 1.90), P=0.22, I-2 = 61%). Compared with no treatment, TCM seemed to increase the treatment success rate (UPSIT) (RR = 3.17, 95% CI (1.78, 5.65), P < 0.0001, I-2 = 0%), but there was no statistically significant difference in improving the UPSIT score (MD = 3.44, 95% CI (-1.36, 8.24), P=0.16). Compared with drug therapy, TCM plus drug therapy appeared to increase the effective rate (delta VAS) (RR = 2.36, 95% CI (1.41, 3.94), I-2 = 0%), but there was no statistically significant difference in improving the TDI score (MD = 2.10, 95% CI (-1.99, 6.19), P=0.31). No significant differences in adverse reactions were reported between TCM and OTDT. Conclusion. TCM may be an effective treatment for PVOD. With a lack of high-quality RCTs, further large-scale and high-quality RCTs are still warranted.