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SCENTinel 1.2 is a rapid smell test developed in the US to detect smell loss in population surveillance (Parma et al., 2021). It is composed of four subtests: odor detection, intensity, identification and hedonic range (Hunter et al., in preparation). Odor identification and hedonic evaluation of the oodors are strongly dependent on the familiarity with such odors, and as a result cultural differences are known to impact the measurement of olfactory abilities. Here, we test the accuracy of 9 versions of the rapid smell test SCENTinel 2.2 in a population of healthy adults and a group of participants with anosmia in Benin City, Nigeria. We compare their results with a group of adults from the US to identify culture-specific differences in the test response patterns. Our main aims with this preregistration are: 1. We will compare the outcome of the odor detection SCENTinel subtest separately between people with normosmia and anosmia in Nigeria. 2. We will compare the outcome of the odor intensity SCENTinel subtest separately between people with normosmia and anosmia in Nigeria. 3. We will compare the outcome of the odor identification SCENTinel subtest separately between people with normosmia and anosmia in Nigeria. 4. We will compare the outcome of the odor hedonic range SCENTinel subtest separately between people with normosmia and anosmia in Nigeria. 5. We will compare the outcome of the overall SCENTinel test separately between people with normosmia and anosmia in Nigeria. 6. We will compare the test-retest reliability to the overall SCENTinel test in people with normosmia in Nigeria. 7. We will compare the outcome of the odor detection SCENTinel subtest between people with normosmia in Nigeria and in the US. 8. We will compare the outcome of the odor intensity SCENTinel subtest between people with normosmia in Nigeria and in the US. 9. We will compare the outcome of the odor identification SCENTinel subtest between people with normosmia in Nigeria and in the US. 10. We will compare the outcome of the overall SCENTinel test between people with normosmia in Nigeria and in the US. 11. We will compare the outcome of the overall SCENTinel test between people with anosmia in Nigeria and in the US.

Loss or impaired sense of smell is a symptom of viral illnesses, including the common cold (Pellegrino et al., 2017) and SARS-CoV-2 (Gerkin et al., 2020; Pellegrino et al., 2020), sinonasal disease (Dalton, 2004), traumatic brain injury (Collet et al., 2009), drugs or toxins (Schiffman, 2018; Upadhyay & Holbrook, 2004), neurodegenerative diseases (Ponsen et al., 2009; Solomon, 1994), surgery (Deems et al., 1991), and chemotherapy (Amézaga et al., 2018), among others (Nordin & Brämerson, 2008). Prior to 2020, over 200,000 people sought treatment for olfactory impairment annually (Pellegrion et al., 2020), primarily caused by viral illnesses (Dalton, 2004). COVID-19 has increased the known prevalence for post-viral smell loss by ~30% (Hummel et al., 2016), and ~20% for all forms of smell loss (Hannum et al., 2020; Liu et al., 2016; Mullol et al., 2012). However, subjective measurements may underestimate the true prevalence of smell loss by about 26% (Hannum et al., 2020) in part due to general lack of awareness of chemosensory changes in the general population. Objective measurements can more accurately identify changes in smell function, but are not always feasible due to scaling, time or budget constraints (Parma et al., 2021). Yet they represent the best way to track recovery from smell loss. A quick recovery would minimize the negative effects associated with smell loss, such as a reduced quality of life (Boesveldt et al., 2017), depression (Rochet et al., 2018), malnutrition (Gopinath et al., 2016) and exposure to toxins such as smoke and natural gas (Pence et al., 2014). However, the time to recovery is variable: 85% of people recover from post-COVID smell loss within 3 weeks (Cecchetto et al., 2021; Chiesa-Estomba et al., 2020; Reiter et al., 2020; Vaira et al., 2020), while 15% of people do not recover and their smell loss persists long after the rest of their COVID-19 symptoms subside (Borsetto et al., 2020; Cecchetto et al., 2021; Chiesa-Estomba et al., 2020; Vaira et al., 2020). Others with post-viral smell loss have reportedly taken years to recover (Lee et al., 2014). Other etiologies of smell loss may also have longer or more permanent effects on smell loss, such as traumatic brain injury (Reden et al., 2006) or neurodegenerative diseases (Hummel et al., 2016; Whitcroft et al., 2017). Recovery may also differ depending on age and sex of the person (Amer et al., 2020; Lee et al., 2014; Mullol et al., 2012). There is currently no cure for smell loss, however some interventions have been effective in improving smell recovery, such as olfactory training (Sorokowska et al., 2017) and pharmacological interventions (Hummel et al., 2016; Yan et al., 2019). Due to the rapid influx of studies assessing smell loss from COVID-19, the time is mature for a metanalytic analysis to synthesize the factors influencing recovery from post-viral smell loss, and compare it recovery following smell loss due to other etiologies (e.g. post-traumatic, neurodegenerative, sinonasal, toxins, surgery, and chemotherapy). A comprehensive analysis of recovery from smell loss due to COVID-19 and how it compares to other etiologies of smell loss does not currently exist. The aim of the study is to determine the recovery prevalence and recovery time from smell loss based on the available literature. Etiology of smell loss, time since etiological event (for prevalence), type of test (subjective vs objective), presence/absence of an intervention, type of intervention, age, and sex will be used as moderators. With this literature search and analysis, we will answer the following experimental questions if data from 4 or more articles per condition can be included: 1. What is the prevalence (percent) of smell loss recovery overall (all etiologies with minimal intervention combined)? 2. What is the prevalence (percent) of smell loss recovery from post-COVID smell loss compared to other etiologies of smell loss (if 4 or more articles are available per etiology). 3. How does the prevalence (percent) of smell loss recovery differ among etiologies of smell loss (if 4 or more articles are available per etiology). ● Exploratory analysis: How does the prevalence (percent) of smell loss recovery differ among acute (12 weeks) cases of smell loss (if >4 of each case are available). 4. Does the prevalence (percent) of smell loss recovery differ based on type of assessment (objective vs. subjective)? 5. Do certain demographics (age and sex) have a higher prevalence (percent) of smell loss recovery than others? 6. Do interventions improve smell loss recovery prevalence (percent)? 7. What is the recovery time (days) from smell loss overall (all etiologies with minimal intervention combined)? 8. What is the recovery time (days) from post-COVID smell loss compared to other etiologies of smell loss (if 4 or more articles are available per etiology). 9. How does the recovery time (days) from smell loss differ among etiologies of smell loss (if 4 or more articles are available per etiology). ● Exploratory analysis: How does the recovery time (days) from smell loss differ among acute and chronic cases of smell loss (if >4 of each case are available). 10. How does the recovery time (days) from smell loss differ based on type of assessment (objective vs. subjective)? 11. Do certain demographics (age and sex) have a reduced recovery time (days) from smell loss than others? 12. What is the impact of interventions on recovery time (days) from smell loss? Recovery includes any reported improvement in smell function.

This study aims at validating a novel rapid smell test to be used in the surveillance of COVID-19. The specific goals of this validations are the following: 1. Validate the accuracy of the rapid smell test against a gold-standard test, the NIH Olfactory toolbox in normosmics 2. Characterize the response patterns of individuals with pre-existing smell disorders to the rapid smell test

We know that studying smell and taste loss in children and adolescents may be challenging, and as a result it is an understudied phenomenon (Schriever et al., 2018) . Sudden smell and taste loss is a prominent and prevalent symptom of COVID-19 in adults, which can be harnessed for early detection of the disease and to control the spread of the infection (Gerkin et al., 2021; Menni et al., 2020).). Though it is unclear whether smell and taste loss have been harnessed as a symptom of COVID-19 in children and adolescents. With this meta-analysis, we aim to answer the following questions: 1. Are smell and taste loss a symptom assessed in relation to COVID-19 in children and adolescents? 2. If so, are subjective ratings mainly used to determine smell and taste loss? Who provides the report: children, parents, healthcare professionals? 3. Given that relying on subjective smell and taste ratings in adults with COVID-19 underrepresents the prevalence of smell and taste loss in the population (Hannum et al., 2020), can we quantify whether this happens in children and adolescents?

We have developed SCENTinel, a rapid smell test, that consists of three subtests: odor detection, odor intensity, and odor identification (Parma et al., 2020). Each SCENTinel test comprises of three odor patches, one that includes a scented odor, the other two unscented. We have currently four different odorant versions of the SCENTinel test. Recently, we validated the use of SCENTinel, a rapid smell test, against a gold-standard test, the NIH Toolbox(R) Olfactory Test in a normosmic (normal ability to smell) population (Parma et al. 2020). Additionally, SCENTinel was able to characterize individuals with pre-existing smell disorders (anosmia) compared to normosmics, and to a certain extent, individuals with other smell disorders. The present study aims at further validating SCENTinel with these specific goals: 1. Characterize the SCENTinel response patterns for participants with quantitative smell disorders (e.g., anosmia, hyposmia), qualitative smell disorders (e.g., parosmia, phantosmia), those with simultaneously both quantitative and qualitative smell disorders, as well as normosmics (those without a smell disorder). 2. Investigate SCENTinel performance across four different odor versions of SCENTinel in the normosmic group. 3. Explore the hedonic range of the tested odors for participants reporting qualitative smell disorders (e.g., parosmia, phantosmia).

This is a correction notice for article bjaa041 (DOI: https:// doi.org/10.1093/chemse/bjaa041), published 20 June 2020. An incorrect version of the caption to Figure 5 was mistakenly included in the published paper. An updated version is given below. Neither the data nor the paper's conclusions were affected by this correction. The authors sincerely apologize for the error. (A) Correlations between the 3 principal components with respect to changes in 3 chemosensory modalities (i.e., taste, smell, and chemesthesis). Shades of gray indicate positive correlation, whereas shades of red indicate negative correlations. White denotes no correlation. (B) Clusters of participants identified by k-means clustering. The scatterplot shows each participant's loading on dimension 1 (degree of smell and taste loss, PC1 on x-Axis) and dimension 2 (degree of chemesthesis loss, PC2 on y-Axis). Based on the centroid of each cluster, participants in cluster 1 (blue, N = 1767; top left) are generally characterized by significant smell, taste and chemesthesis loss. Participants in cluster 2 (orange, N = 1724; bottom center) are generally characterized by ratings that reflect smell/taste loss with preserved chemesthesis. Loadings for participants in cluster 3 (green, N = 548; right side) are generally characterized by reduced smell and taste loss, and preserved chemesthesis.