Olfactory dysfunction (OD) has long been considered a symptom of COVID-19, but its use in COVID-19 testing can be questionable, as subjective olfactory tests can significantly underreport OD. A new prospective, cross-sectional research letter from researchers at Southern Methodist University in Dallas has examined the utility of objective olfactory testing to determine COVID-19 status (JAMA Otolaryngol Head Neck Surg. Published online July 15, 2021. doi:10.1001/jamaoto.2021.1456. The work was supported by SAFER Diagnostics).
This study enrolled 163 healthy adults from a single college campus COVID-19 screening site. Participants were screened for OD using a novel scent card (SAFER Diagnostics) followed immediately by polymerase chain reaction (PCR) testing for COVID-19 from nasopharyngeal swabs. The card contained a single scent in a scratch-and-sniff label that the participant identified from eight options: lemon, grape, floral, blueberry, banana, mint, unsure, or no scent. Answers were processed electronically using a QR code, and an incorrect choice was classified as OD. Of the 163 participants, 16 tested positive for COVID-19 through PCR test.
Researchers found that 75% (n=12) of the 16 who tested positive for COVID-19 failed the objective OD compared with 4.8% (n=7) among the 147 who tested negative for COVID-19. Of the 75% of participants who tested positive for COVID-19 and failed the objective OD screening, only 37.5% (n=6) reported subjective anosmia. Taken alone, olfactory screening was the greatest predictor of a positive COVID-19 test when compared with other symptoms, including cough, fever, fatigue, and previous COVID- 19 exposure. The authors cautioned that combined OD screening and other COVID-19 symptom screening can increase sensitivity.