METHODS: We searched the PubMed and Google Scholar on 15th May 2020, with search terms including SARS-COV-2, coronavirus, COVID-19, hyposmia, anosmia, ageusia and dysgeusia. The articles included were cross sectional studies, observational studies and retrospective or prospective audits, letters to editor and short communications that included a study of a cohort of patients. Case reports, case-series and interventional studies were excluded.
DISCUSSION: A total of 16 studies were selected. Incidence of smell and taste dysfunction was higher in Europe (34 to 86%), North America (19 to 71%) and the Middle East (36 to 98%) when compared to the Asian cohorts (11 to 15%) in COVID-19 positive patients. Incidence of smell and taste dysfunction in COVID-19 negative patients was low in comparison (12 to 27%). Total incidence of smell and taste dysfunction from COVID-19 positive and negative patients from seven studies was 20% and 10% respectively. Symptoms may appear just before, concomitantly, or immediately after the onset of the usual symptoms. Occurs predominantly in females. When occurring immediately after the onset of the usual symptoms, the median time of onset was 3.3 to 4.4 days. Symptoms persist for a period of seven to 14 days. Patients with smell and taste dysfunction were reported to have a six to ten-fold odds of having COVID-19.
CONCLUSION: Smell and taste dysfunction has a high incidence in Europe, North America, and the Middle East. The incidence was lower in the Asia region. It is a strong risk factor for COVID-19. It may be the only symptom and should be added to the list of symptoms when screening for COVID- 19.
Materials and Methods: The odorant descriptors and distractors of the original version of Sniffin' Sticks were translated into Malay language. It was then tested for familiarity and identifiability in 30 normosmic subjects. The descriptors were replaced until the familiarity of all descriptors and identification rates of odorants achieved ≥ 70%. The validity of the new cultural-adapted version was tested in 60 hypo-anosmic subjects and 60 normosmic subjects with Student t-test. The test-retest reliability was evaluated after two weeks with interclass correlation.
Results: Two odorant descriptors and nine distractors achieved familiarity <70% (13.3% - 66.7%) and were replaced. Another three culturally inappropriate distractors were also replaced. The mean score among the healthy subjects was significantly higher than the subject with smell dysfunction [13.7 (1.12) and 7.3 (3.42); t = 7.24 (df = 34.23), P<0.001]. The coefficient of correlation (r) between test and retest scores was 0.93 (P<0.001).
Conclusion: The cultural adapted Malaysian version of Sniffin' Sticks smell identification test is valid and has high test-retest reliability. This is the first smell identification test validated in Malaysia. It is effective for evaluation of olfactory function in local population.