Gaining Back What Is Lost: Recovering the Sense of Smell in Mild to Moderate Patients After COVID-19

Abstract

The purpose of our cohort study was to quantify olfactory deficits in COVID-19 patients using Sniffin’ Sticks and a pre-post design to evaluate olfactory recovery. 30 adult patients with laboratory-confirmed mild to moderate forms of COVID-19 underwent a quantitative olfactory test performed with the Sniffin’ Sticks Test (SST, Burghardt®, Wedel, Germany) considering olfactory threshold (T), odor discrimination (D) and odor identification (I). Results were presented as a composite TDI score (range 1–48) used to define functional anosmia (TDI ≤ 16.5), hyposmia (16.5 <TDI< 30.5) or functionally normal ability to smell (TDI ≥ 30.5). Patients also self-evaluated their olfactory function by rating their ability to smell on a visual analogue scale (VAS rating) and answering a validated Italian questionnaire (Hyposmia Rating Scale-HRS). Patients were tested during hospitalization and about two months after symptoms onset. During the hospitalization the overall TDI score indicated that our cohort had impairments in their olfactory ability (10 % was diagnosed with Anosmia and more than 50 % were hyposmic). Almost all patients showed a significant improvement at around one month following the first test and for all the parts of the SST except for odor identification. None of the subjects at one month was still diagnosed with Anosmia. We also quantified the improvement in the TDI score based on initial diagnosis. Anosmic subjects showed a greater improvement than hyposmic and normosmic subjects. In conclusion, within a month time window and two months after symptoms’ onset, in our cohort of patients we observed a substantial improvement in the olfactory abilities.

Sustained Chemosensory Dysfunction during the COVID-19 Pandemic

“…In late March 2020, the UK-based charity AbScent launched the Facebook group “COVID-19 Smell and Taste Loss.” Due to a deluge of members with persistent CD, this group exceeded 9,000 members in early October 2020. Recent studies indicate that both subjective and objectively measured chemosensory function can be affected several weeks after recovery from other COVID-19 symptoms [ 9 , 13 , 14 , 15 , 16 ].…”

From loss to recovery: how to effectively assess chemosensory impairments during COVID-19 pandemic

“…Participants who experienced a more severe chemosensory loss might tend to overestimate their recovery. Other studies which used objective testing methods, also observed a similar dependency between loss and recovery, strengthening the evidence that a greater olfactory improvement post-infection is more likely in patients experiencing sudden anosmia or ageusia during the viral infection than in those experiencing hyposmia and hypogeusia 27,29 .…”

“…Chemosensory disorders are both early and specific symptoms of COVID-19 [24][25][26] . Previous studies indicated that the timeframe for a full or partial recovery (in particular of the sense of smell) seems to be highly variable, spanning from 8 days to even 8 weeks 3,[27][28][29][30][31][32] . For the vast majority of patients (up to 85%), chemosensory issues resolve along with Covid-Like-Illness (CLI) symptoms, in approximately three weeks [31][32][33][34][35] .…”

Sensory disruption and sensory inequities in the Anthropocene

“…For hyposmia linked to sinonasal disease, use of corticosteroids has shown promise 106 . COVID‐19 related olfactory dysfunction is variable in intensity (usually coupled with taste dysfunction) and persistence after the virus clears the body 114 . For other causes of hyposmia, the only treatment is smell training, which improves cognitive processing of odors and appears to improve odor identification but does not restore the sense of smell 115 …”