Singapore’s home test catches smell, taste loss in COVID-19 patients

The Singapore Smell and Taste Test (SSTT), a personal testing kit for the daily home- and self-assessment of smelling and tasting functions, can objectively assess sensory losses in patients with the coronavirus disease 2019 (COVID-19) and align well with self-reported measures of sensory function, according to a recent study.

“The SSTT has potential for future application in populations with limited access to formal COVID-19 testing as a self-administered objective method to monitor sudden changes in smell and taste, and to prompt early self-isolation, in order to reduce community transmission of COVID-19,” the researchers said.

Ninety-nine participants were enrolled in the present study and reported recent changes in sensory ability using a self-accomplished questionnaire. Seventy-two individuals tested positive for COVID-19 at baseline, of whom 58 completed the SSTT at home. The outcome was the agreement between the SSTT’s objective composite scores and the participants’ self-reported smell and tase function, as measured by linear regression models.

SSTT results showed that at day 1, 22 participants demonstrated objective smell and/or taste loss, of whom 21 were positive for COVID-19. Both sensory functions were impaired in 17 positive patients. [Food Qual Prefer 2022;97:104482]

Of the 21 COVID-19-positive patients with objective sensory loss, only 16 reported so on the self-accomplished questionnaires. Nevertheless, the researchers reported significant correlations between first-day composite scores on the objective and self-reported tests for both smell (B, 0.91, 95 percent confidence interval [CI], 0.73–1.05; p=0.001) and taste (B, 0.73, 95 percent CI, 0.42–0.94; p=0.001) functions.

Notably, 60 patients (83.3 percent) who tested positive for COVID-19 reported experiencing no sensory loss symptoms within the last 24 hours at baseline. Similarly, the Sino-Nasal Outcome Test showed that 86.1 percent of positive patients either had no sino-nasal problems or only experienced reduced concentrations.

“These objective smell and taste measures identified losses in smell and taste sensitivity among COVID-19 positive participants and aligned with self-report measures of smell and taste function,” the researchers said. “Our preliminary findings also provide initial insights into the lack of symptoms experienced by those with a mild SARS-CoV-2 infection who were otherwise healthy.”

The SSTT provides each patient with a smell and taste kit. The smell test involves a food (mango) and nonfood (detergent) odour pen, while the taste kit includes four food-grade powders, each corresponding to the four basic tastes: sweet (table sugar), salty (table salt), bitter (granulated coffee powder), and sour (lime powder). Visual analogue scales were used to assess the intensity of the stimuli.

“The current study presents the first application of SSTT to objectively measure smell and taste function among COVID-19 positive participants,” the researchers said.

“Individual early diagnostic measures, such as the SSTT, will support national efforts in containing the spread of COVID-19 and reducing the emergence of clusters of infections as restrictions ease and population vaccination efforts are underway,” they added.