Olfactory dysfunction (OD) can have important effects on QOL for patients and serves as a preclinical marker of neurocognitive diseases. In addition, OD has been identified as a marker for COVID-19. “One of the key symptoms of COVID-19 is loss of smell,” notes Jay F. Piccirillo, MD, FACS. “Unfortunately, current tests for OD are time-consuming, expensive, and must be performed at a doctor’s office.”

The University of Pennsylvania Smell Identification Test (UPSIT) is commonly used to detect OD, but this 40-question assessment is time-consuming and requires a clinician to interpret results. The Sniffin’ Sticks smell test is more elaborate than UPSIT and helps detect and discriminate odor thresholds, but a trained clinician must administer it. Considering these limitations, it is important to develop better tools to detect the presence and extent of OD, according to Dr. Piccirillo.

Dr. Piccirillo and colleagues conducted a study—published in JAMA Otolaryngology-Head & Neck Surgery—in which they developed and validated the Novel Anosmia Screening at Leisure (NASAL). “This self-administered, at-home diagnostic smell test is intended to be a cost-effective approach to screen people for OD using commonly found household items,” says Dr. Piccirillo. Two versions of NASAL were developed by consolidating 45 household items from other OD tests. NASAL-7 has seven items and NASAL-3 has three items (Table), with each item scored as 0 for cannot smell, 1 for smells less strong/different than normal, or 2 for smells normal. The total NASAL score is the sum of each item score. The NASAL-7 score can range from 0-14, whereas NASAL-3 is scored from 0-6, with lower scores indicating greater anosmia.

 

NASAL Tests Are Easy to Use, Effective & Inexpensive

The study, which included 115 participants with self-reported OD, showed that both the NASAL-7 and NASAL-3 were moderately accurate for identifying anosmia. Scores of 7 or lower on NASAL-7 correlated with 70% sensitivity and 53% specificity in discriminating patients with anosmia from those without loss of smell. Scores of 2 or lower on the NASAL-3 correlated with 57% sensitivity and 78% specificity in discriminating anosmia. There was moderate agreement between UPSIT-defined OD categories and those defined by NASAL-7 and NASAL-3. Agreement with self-reported severity of OD was also moderate for both NASAL tests.

The NASAL assessments address limitations with other OD assessments in that they are inexpensive and brief, according to Dr. Piccirillo. “NASAL assessments can test patients’ ability to smell items at normal odor concentrations and allows them to report when items smell less strong or different,” he says. “Ease of administration is another important benefit. NASAL-7 and NASAL-3 can be performed and scored at home by patients without help from a clinician. Items on the NASAL tests are usually available in the home, meaning the screening can be administered universally to all types of patients.”

 

Identifying Differences Between NASAL Tests

The NASAL-7 and NASAL-3 screenings each contribute unique information for patients who test their sense of smell. “NASAL-7 should be used whenever possible, but NASAL-3 can be offered to patients who don’t have all 7 items from NASAL-7 available in the home,” says Dr. Piccirillo. NASAL-7 takes about 3-10 minutes to complete, whereas the NASAL-3 takes 1-5 minutes. NASAL-7 correlated more strongly with other OD screening tools and was slightly more accurate in detecting anosmia and normosmia than NASAL-3. In addition, NASAL-7 can discriminate between severe and mild OD cases.

Additional research is needed to externally validate NASAL-7 and NASAL-3, according to Dr. Piccirillo. “Future research should seek to define the sensitivity of these tests to changes over time as well as test-retest reliability,” he says. “Studies should also explore if NASAL-7 and NASAL-3 can be used to screen for neurocognitive disorders and perhaps as a diagnostic or prognostic tool for COVID-19–associated OD. These tests might also be useful in clinical trial settings conducted virtually. In the meantime, clinicians should consider using NASAL assessments more routinely as a convenient and inexpensive approach to screening patients for OD.”

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