Table 2

Non-drug treatment options for post-viral olfactory dysfunction

AuthorYearStudy designNo of participantsInterventionMeasuresOutcomesNumerical results
Pires et al992022Randomised, controlled80Classical olfactory training, four odours; advanced olfactory training, eight odours; olfactory training for 4 weeksUniversity of Pennsylvania Smell Identification test, visual analogue scaleScore improvement in University of Pennsylvania Smell Identification testPost-intervention improvement: advanced olfactory training=1 (range -7 to 10, interquartile range 4); classical olfactory training=1.7 (-7 to 12, 5); P=0.28
Vandersteen et al1002022Prospective cohort43Olfactory training for 6 monthsSniffin' Sticks test; SF-36 questionnaireSniffin' Sticks test threshold discrimination identification improvementPre-intervention mean score 24.7 (standard deviation 8.9), post-intervention mean score 30.9 (9.8); P<0.001
Choi et al1012021Non-randomised, controlled104Olfactory training for 3 months v no olfactory trainingSniffin' Sticks test; visual analogue scaleIdentification improvement in Sniffin' Sticks test threshold discriminationPre-intervention scores: olfactory training 17.5 (standard deviation 6.1) v no olfactory training 15.6 (6.5), P=0.14; post-intervention scores: olfactory training 22.1 (6.8) v no olfactory training 18.3 (5.6), P=0.003
Altundag et al1022015Non-randomised, controlled85Classical olfactory training with four odours; modified olfactory training with 12 odours; no olfactory training; intervention performed for 36 weeksSniffin' Sticks test, visual analogue scaleIdentification improvement in Sniffin' Sticks test threshold discriminationPre-intervention mean scores: classical olfactory training 18.1; modified olfactory training 18.2; no olfactory training 18; F(76)<1.82; P>0.16. Post-intervention mean scores: classical olfactory training 26.3; modified olfactory training 24.3; no olfactory training 19.7; F(246)>11.9, P<0.001
Damm et al1032014Randomised, single blind, controlled, crossover144High odorant concentration olfactory training v low concentration olfactory training for 16 weeks; groups crossed over after 16 week periodSniffin' Sticks test, visual analogue scalePercentage of patients with improvement in Sniffin' Sticks test threshold discrimination identificationHigh concentration olfactory training improvement 25.7%; low concentration olfactory training 14.9% (P=0.11) at 16 weeks; crossover period: improvement in low to high olfactory training 30.8%; high to low olfactory training 45.8% (P=0.07)
Liu et al1142021Retrospective cohort153Olfactory training with subgroup analysis of patients with parosmiaSniffin' Sticks testClinically relevant recovery of overall olfactory function (defined as improvement in threshold discrimination identification of ≥5.5 points)Odds ratio for olfactory improvement 1.12 (95% confidence interval 0.59 to 2.46), P=0.62; threshold 1.11 (0.53 to 2.33), P=0.78, discrimination 2.88 (1.25 to 6.11), P=0.006, identification 3.38 (1.50 to 7.60), P=0.003
  • SF-36=36 item short form survey.