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Response to Alfonso Santamaría-Gadea and Colleagues

with COVID-19 with smell loss via a ‘‘face-validated’’ anosmia reporting tool for clinicians. Face validity is merely a subjective superficial assessment of whether the measurement procedure that you use appears to be valid. The authors reported 73% of anosmia occurring before the diagnosis of COVID-19. This percentage was inadequately used as OD prevalence in the Tong et al forest plot. The second study, by Moein et al, reported an alarming 98% prevalence of OD in confirmed COVID-19 cases among Iranian patients. They used the University of Pennsylvania Smell Identification Test (UPSIT), a well-validated psychophysical smell test in an American population. However, the UPSIT has been demonstrated not to be valid for an Iranian population due to a large number of unfamiliar odors. Indeed, a modified UPSIT exists with different normative values for Persian population that includes only 24 of the 40 original odorants. The third study, by Lechien et al, showed an 85% prevalence of OD based on a short version of the Questionnaire of Olfactory Disorders–Negative Statements. To our knowledge, this questionnaire is validated only in German and English languages; however, the authors included nativespeaking patients from France, Belgium, Spain, and Italy. Tong et al placed special emphasis on these 3 articles in their meta-analysis. However, on the basis of the evidence mentioned here, we think that the authors may yield false results by overestimating OD prevalence in patients with COVID-19. Meta-analyses are powerful scientific tools used to condense findings from individual studies, and their popularity is hence increasing. However, their validity depends on the quality of studies involved; thus, publication of prevalence numbers is nice but ultimately pointless if the quality of primary data is low and heterogeneous.