The Association Between Neurocognitive Disorders and Gustatory Dysfunction: A Systematic Review and Meta-Analysis.

Olfactory and gustatory dysfunction have been reported in mild and major neurocognitive disorders (NCDs), with variable results. While olfactory dysfunction has been consistently explored, reports on gustatory alterations are limited. We systematically reviewed case-control studies evaluating gustatory function in NCDs with various etiologies and different neuropathology. Eighteen studies were included in the systematic review, and eight were included in the meta-analysis. Most studies were on Alzheimer's disease (AD) and Parkinson's disease (PD). Pooled analyses showed worse global taste threshold and identification (sour in particular) scores in AD than controls and worse global, sweet, and sour scores in AD compared to mild cognitive impairment (MCI). PD with MCI showed worse global, sweet, salty, and sour scores than controls and cognitively unimpaired PD. Taste dysfunction was differentially associated with the severity of cognitive deficits. Gustatory dysfunction may represent a potential cross-disease chemosensory biomarker of NCD. Whether gustatory alterations may be a pre-clinical biomarker of NCD requires further studies.

Therapy-Associated Saliva and Taste change Evaluation (TASTE) in head & neck cancer patients undergoing radiotherapy: a study protocol.

BACKGROUND: One of the main side effects of radiation therapy to the head and neck region is altered taste sensation. This causes significant morbidity and has profound effects on the quality of life (QoL) of patients. While radiation-associated toxicities like xerostomia and dysphagia are part of large investigations, data on taste impairment is sparse. Small cohort sizes in the majority of studies and a variety of analysis methods limit our current understanding of the underlying processes. None of the studies published to date used a taste-specific QoL questionnaire with differentiation of the different taste qualities (e.g. sour, bitter). Furthermore, data regarding the correlation of taste impairment with radiation-associated change in saliva composition is currently not available. The aim of the TASTE study is to fill this gap. Based on the acquired data, a normal tissue complication probability (NTCP) model for late radiation-associated taste impairment will be developed. METHODS: In this prospective, observational multicenter study 150 head and neck cancer patients undergoing radiation therapy will be recruited and undergo repetitive (semi-) objective and subjective assessment of their taste, smell and salivary function (questionnaires, taste and smell assessment, saliva analysis). Primary endpoint will be patient-reported taste impairment 12 months post radiation therapy using a standardized questionnaire. Secondary endpoints will include taste impairment measured using taste strips at 12 months and 2 years post radiation therapy. Differences between subgroups (radiation side, chemotherapy, etc.) and changes over time will be assessed while adjusting for confounding factors (e.g. age, sex, smoking history). DISCUSSION: This study sets out to further our understanding of taste impairment in patients undergoing radiation therapy to the head and neck region with the goal to prevent this common side effect in future patients. The results of the study may be used to evaluate taste-preserving radiotherapy for patients with head and neck cancer, which may significantly reduce the long-term burden in this patient cohort.

Integrating the patient's voice into the research agenda for treatment of chemosensory disorders.

World-wide some 658 million people were infected with coronavirus disease 2019 (COVID-19) and millions suffer from chemosensory impairment associated with long COVID. Current treatments for taste and smell disorders are limited. Involving patients has the potential to catalyze the dynamic exchange and development of new ideas and approaches to facilitate biomedical research and therapeutics. We assessed patients' perceptions of the efficacy of treatments for chemosensory impairment using an online questionnaire completed by 5,815 people in the US Logistic regression determined variables predictive of reported treatment efficacy for patients aged 18 to 24, 25 to 39, 40 to 60, and 60+ yrs. who were treated with nasal steroids, oral steroids, zinc, nasal rinse, smell training, theophylline, platelet-rich plasma, and Omega 3. The most consistent predictor was age, with the majority of those 40 to 60 and 60+ reporting that nasal steroids, oral steroids, zinc, nasal rinse, and smell training were only slightly effective or not effective at all. Many of these treatment strategies target regeneration and immune response, processes compromised by age. Only those under 40 reported more than slight efficacy of steroids or smell training. Findings emphasize the need to include patients of all ages in clinical trials. Older adults with olfactory impairment are at increased risk for Alzheimer's disease (AD). We speculate that olfactory impairment associated with long COVID introduces the potential for a significant rise in AD. Long COVID-associated chemosensory impairment increases the urgency for translational and clinical research on novel treatment strategies. Suggestions for high-priority areas for epidemiological, basic, and clinical research on chemosensory impairment follow.

Brochure intervention to manage bothersome taste changes in pediatric patients receiving cancer therapy.

BACKGROUND: Primary objective was to determine if a patient informational brochure describing potentially useful strategies could help manage specific taste changes. Secondary objective was to describe the specific strategies used and whether the strategies were perceived as being helpful. PROCEDURE: This single-center study included pediatric patients with cancer or hematopoietic cell transplant recipients receiving active treatment who experienced bothersome taste changes in the last month. Participants participated in baseline and follow-up interviews conducted 14-21 days apart. A brochure that listed 16 potentially helpful strategies was provided at baseline. At follow-up, we asked about brochure use and whether it helped. At both interviews, we asked about experienced taste changes, strategies used, and whether strategy helped. RESULTS: Of 100 enrolled participants, different (87%) and bad (72%) taste were most common at baseline. Following the brochure intervention, statistically significant reductions were observed in food tasting different, bad, bland, bitter, sour, and metallic. For most strategies, the proportion of patients who used specific strategies or found them helpful was not significantly different between baseline and follow-up. However, "eating foods you like" was considered helpful in significantly more participants who used the strategy in follow-up (72 out of 89, 80.9%) compared with baseline (55 out of 95, 57.9%; p = .008). Between visits, 81.2% looked at the brochure. Among participants, 53.1% found the brochure helpful, very helpful, or extremely helpful. CONCLUSIONS: A brochure that offered strategies to manage changes in taste helped participants cope with them. Further research should evaluate the brochure using randomized and multicenter trials.

Taste disorders and alopecia in myasthenia gravis.

BACKGROUND: Non-motor symptoms in myasthenia gravis (MG) are rarely confirmed. Although there are some small cohort studies, a large-systemic survey has not yet been performed. METHODS: We investigated the incidence and clinical characteristics of patients with MG who had taste disorders and alopecia using data of 1710 patients with MG enrolled in the Japan MG Registry 2021. RESULTS: Among them, 104 (6.1%) out of 1692 patients and 138 (8.2%) out of 1688 patients had histories of taste disorders and alopecia, respectively. Among the patients with MG, taste disorders were significantly more common in women, those with severe symptoms, refractory MG, or thymoma-associated MG, and were less common in those with ocular MG. The taste disorders often occurred after the onset of MG and often responded to MG treatments. Alopecia was more common in MG patients with a history of bulbar palsy and thymoma, and it often occurred before the onset of MG and sometimes responded to MG treatments. Multivariate logistic regression analysis revealed taste disturbance was associated with worst quantitative MG score and thymoma-associated MG; and alopecia was associated with thymoma-associated MG. CONCLUSION: Clinicians should be aware of the non-motor symptoms in MG, especially in patients with severe myasthenic symptoms and thymoma-associated MG.

Determination of objective taste perception among Iranian medical sciences students during COVID­19 pandemic in Yazd, Eastern Iran: a case-control pilot study.

BACKGROUND: Taste disorders in patients suffering from COVID-19 were popular. Some people even after recovery report residual effects of loss of smell and taste. This study aimed to investigate the taste Perception of Iranian Medical Sciences students during the COVID-19 pandemic. METHODS: The case-control study evaluated 50 Medical Sciences students with a history of COVID-19 infection, as confirmed by the Novel Coronavirus (2019-nCOV) CFX96™ Real-Time PCR Detection System. The other participants consisted of 50 volunteer students with COVID-19 negative. The taste perception was measured with 4 different concentrations of the basic tastes. The stimuli were applied to the protruded tongue. Subjects were asked to identify the researcher when they felt the taste. Data are expressed as frequency distribution and analyzed with the Chi-Square test (P < 0.05). RESULTS: In this survey, 54% of participants were male and 46% were female, the mean age of participants was 22.96 ± 5 years. The results showed a significant difference in the sweet and bitter taste perception score according to the history of dietary supplement use. The bitter taste perception score declared a considerable difference since COVID-19 infection. There was no significant difference between the taste perception in the two studied groups for all 4 basic tastes according to gender, COVID-19 infection status, history of taste and smell disorders, and the elapsed time since COVID-19 infection. CONCLUSION: Our findings could provide important insights into taste perception. The history of dietary supplementation may influence how sweetness and saltiness are perceived. There was a noticeable difference in bitter taste perception depending on the time that had elapsed since the most recent COVID-19 infection.

Taste alterations after hematopoietic cell transplantation: a scoping review.

PURPOSE: This review aimed to evaluate the prevalence and characteristics of dysgeusia after hematopoietic cell transplantation (HCT). METHODS: A literature search (in PubMed, Embase.com and Web of Science) for clinical studies evaluating taste before and after HCT was performed up to June 22, 2023, in collaboration with a medical information specialist. After title and abstract review (N = 807) followed by full-text review (N = 61), articles that met the inclusion criteria were summarized in a table and synthesized narratively. RESULTS: 11 articles were analyzed in this review. All studies had a prospective design and patient populations included children (N = 3) and adults (N = 8) undergoing allogeneic or autologous HCT. Taste was assessed objectively (N = 6) and/or subjectively (N = 8) between baseline and 12 months after HCT. Before HCT, the self-reported (0-31%) and objective (2.4-10%) prevalence of dysgeusia was low. During the neutropenic phase, self-reported (20-100%) and objective (21.4%) dysgeusia was highest. In the post-engraftment period, the self-reported (18%) and objective (0-33%) prevalence of dysgeusia decreased. Different taste qualities were assessed in six studies including salt, sour, bitter, sweet, and umami. CONCLUSIONS: Some patients undergoing HCT experience dysgeusia prior to treatment. During the neutropenic phase, they had highest complaints, with recovery occurring in the post-engraftment period. All basic tastes, except bitter, were affected. Umami and salt were most affected during treatment. These findings have implications for patient management.

The nutritional impact of metallic taste in head and neck cancer patients: explorations and clinical implications.

PURPOSE: Metallic taste (MT) is frequently observed during head and neck cancer treatments, but very little is known about its impact on nutritional status. The aim of this study was to explore the impact of MT on the quality of life and nutritional status in patients with head and neck cancer expressing MT. METHODS: Questionnaires on quality of life, MT, weight, and food intake were filled out by 44 patients with head and neck cancer before, during, and up to 1 year after their treatment. Patients were divided into two groups based on their reported experience of MT. RESULTS: MT was commonly observed (n = 12, 27.2%), always during the treatment phase, and mostly linked with radiotherapy or radiochemotherapy. Reported MT intensity was moderate (n = 6, 40%) to high (n = 4, 26.7%). MT had a significant negative impact on quality of life linked to dysgeusia (p = 0.025). The negative impacts of MT on food intake and on weight were not significant, possibly due to a combination of sample size, dropouts, and duration of observation. Further research in this area could provide additional insights into how to better address the issue related to MT and enhance the quality of care provided to this patient population. CONCLUSION: Metallic taste, experienced by 27.2% of the 44 patients with head and neck cancer, contributes to dysgeusia and results in a significant decline in quality of life associated with dysgeusia. TRIAL REGISTRATION: ClinicalTrials.gov trial registration number: NCT03558789.

Long-term effects of SARS-CoV-2 infection in patients with and without chemosensory disorders at disease onset: a psychophysical and magnetic resonance imaging exploratory study.

A preserved sense of smell and taste allows us to understand many environmental "messages" and results in meaningfully improvements to quality of life. With the COVID-19 pandemic, it became clear how important these senses are for social and nutritional status and catapulted this niche chemosensory research area towards widespread interest. In the current exploratory work, we assessed two groups of post-COVID-19 patients who reported having had (Group 1) or not (Group 2) a smell/taste impairment at the disease onset. The aim was to compare them using validated smell and taste tests as well as with brain magnetic resonance imaging volumetric analysis. Normative data were used for smell scores comparison and a pool of healthy subjects, recruited before the pandemic, served as controls for taste scores. The majority of patients in both groups showed an olfactory impairment, which was more severe in Group 1 (median UPSIT scores: 24.5 Group 1 vs 31.0 Group 2, p = 0.008), particularly among women (p = 0.014). No significant differences emerged comparing taste scores between Group 1 and Group 2, but dysgeusia was only present in Group 1 patients. However, for taste scores, a significant difference was found between Group 1 and controls (p = 0.005). No MRI anatomical abnormalities emerged in any patients while brain volumetric analysis suggested a significant difference among groups for the right caudate nucleus (p = 0.028), although this was not retained following Benjamini-Hochberg correction. This exploratory study could add new information in COVID-19 chemosensory long-lasting impairment and address future investigations on the post-COVID-19 patients' research.

A longitudinal evaluation of smell and taste function in children with cancer during and after treatment with chemotherapy.

Smell and taste changes are bothersome treatment symptoms interfering with food intake. It remains unclear how and when children with cancer experience such changes during chemotherapy, and if the symptoms resolve after treatment. In this longitudinal study, we measured smell and taste function of 94 childhood cancer patients treated for hematological, solid, or brain malignancies. Smell and taste function were assessed using commercial Sniffin' Sticks and Taste Strips, respectively. For both tests, normative values were used to identify the presence of smell and taste abnormalities. Self-reported chemosensory and appetite changes were assessed using a questionnaire. Measurements were taken approximately 6 weeks (T0), 3 months (T1), 6 months after starting chemotherapy (T2), and 3 months after termination of chemotherapy or maintenance phase for children with acute lymphoblastic leukemia (ALL) (T3). We found that smell and taste scores did not change during active treatment (T0-2). However, approximately 20% of the patients suffered from decreased taste function according to normative values, particularly children with lymphoma or solid tumors. Changes in smell were predominantly characterized as increased rather than decreased. Self-reported changes were much more common than objectively measured, with smell changes ranging from 26 to 53% and taste changes up to 80% during treatment. After active treatment, odor threshold scores decreased in children with ALL during maintenance phase, whereas total taste scores increased in all children at T3. In summary, objectively measured smell and taste function remained stable during active treatment, while at the individual level a fairly large number of children suffered from chemosensory distortions which comprised either increased or decreased sensitivity. Individual dietary advice and coping strategies are warranted to prevent detrimental effects on food intake in children with cancer.

Comparison of the incidence of smell and taste disorders between influenza and COVID-19.

OBJECTIVE: Smell and taste disorders among patients with COVID-19 has become increasingly reported in the literature, however the prevalence varies. Post-infectious respiratory dysfunction has also been linked to influenza. In this study, we aimed to compare the rates of smell and taste disorders between COVID-19 and Influenza in unvaccinated patients. STUDY DESIGN: Retrospective cohort study. SETTING: TriNetX research network. METHODS: Two queries were made on 7/1/2023 to include Influenza without a diagnosis of COVID-19 and a COVID-19 without a diagnosis of Influenza. The queries included patients from January 1 to December 31, 2022 from 102 Healthcare Organizations. The resultant population of patients with ICD-10 codes for COVID-19 and Influenza were matched using demographic characteristics to evaluate the risk of smell disorders. RESULTS: The overall 3-month incidence of smell and taste disorders was 0.73 % in the COVID-19 population and 0.1 % in the influenza population. The 3-month matched risk ratios were 11.1 [95 % CI (8.8,13.8)]; p < 0.001) times higher for disorders of the smell and taste secondary to COVID-19 compared to influenza. CONCLUSIONS: Disorders of the smell and taste are more common among patients with COVID-19 compared to patients with Influenza. Beyond smell loss, patients experience additional nasal and sinus-related rhinological symptoms, pointing to COVID-19's and influenza's wider impact on overall rhinological health. We believe that due to the transient nature of these disorders, they might go underreported.

Taste dysfunction after endoscopic endonasal resection of olfactory groove meningioma: Case series and review of the literature.

PURPOSE: The incidence of ageusia and dysgeusia after endoscopic endonasal (EEA) resection of olfactory groove meningioma (OGM) is not well established despite recognized impairment in olfactory function. METHODS: We retrospectively administered a validated taste and smell survey to patients undergoing EEA for resection of OGM at two institutions. Demographics and clinical characteristics were collected and survey responses were analyzed. RESULTS: Twelve patients completed the survey. The median time from surgery was 24 months. The average total complaint score was 5.5 out of 16 [0-13]. All patients reported a change in sense of smell while only 42 % reported a change in sense of taste. Taste changes did not consistently associate with laterality or size of the neoplasm. Significant heterogeneity existed when rating severity of symptoms. CONCLUSIONS: To our knowledge this is the first case series examining taste changes after EEA resection of OGM. Despite universal olfactory dysfunction, only a minority of patients reported a change in their sense of taste. Our findings may improve patient counseling and expectations after surgery.

Predictive factors of involuntary weight loss in patients with smell and taste disorders.

BACKGROUND: Chemosensory dysfunction (olfaction, taste, and trigeminal) affects quality of life, potentially impacting eating behaviors. We investigated which factors are associated with weight loss in patients with smell and taste disorders. METHODS: Retrospective study of consecutive adult patients seen in the smell and taste clinic during a 10-year period. Patients were asked about smell, flavor and taste impairment. Psychophysically, smell was assessed with Sniffin' Sticks, flavor with a retronasal test, and taste with Taste Strips. RESULTS: A total of 554 patients (313 females) were included with a median age of 51 years (IQR 23). Seventy-six (13.7%) reported involuntary weight loss (median 6 kg, IQR 6) due to chemosensory disorders. The odds of losing weight were 2.1 times higher when patients reported subjective changes in flavor perception. Parosmia was a significant predictor of weight loss. Patients with symptoms lasting longer than two years were less likely to present with weight loss. Post-traumatic chemosensory dysfunction was a significant predictor of losing weight. On psychophysical testing, the probability of a patient losing weight increased by 8% for every 1-unit reduction in Taste Strips score. CONCLUSION: Factors associated with weight loss were self-reported changes in flavor perception, parosmia, duration of symptoms for less than two years, head injury, and psychophysically measured low Taste Strips score. These data help to identify patients at risk of weight loss from smell or taste impairment.

Taste loss in COVID-19 â€" psychophysical evidence supporting a low prevalence.

Much - possibly even too much - has been published about chemosensory dysfunction as a consequence of COVID-19. Studies have reported prevalence of taste loss in up to 89.9%, which is in a similar range as COVID-19 related smell loss. However, most of these publications rely solely on patients' self-reports. Only few studies used validated psychophysical tests to specifically address olfaction and gustation. Especially for gustation, it is evident that subjective reporting does not correlate well with more objective psychophysical findings, often leading to an overestimation of subjectively impaired taste.

Association of gustatory dysfunction and Alzheimer.

BACKGROUND: Chemosensory dysfunction has been reported to be involved in the pathogenesis of Alzheimer’s disease (AD). Compared with olfaction, gustatory dysfunction in AD has not been evaluated in depth. We reviewed previously published studies regarding gustatory dysfunction in patients with AD compared with healthy controls. METHODS: A systematic review was conducted by searching the MEDLINE, Cochrane Library, Embase, and PubMed databases covering publications from January 2000 to February 2023. The search was performed using the keyword "Alzheimer* AND (gustatory OR taste OR gustation)." Only studies that performed gustatory function testing and compared the results between patients with AD and healthy controls were included. A random-effects meta-analysis was performed. RESULTS: Twelve articles were finally included, and various gustatory tests including taste strips, the taste disk test, taste solutions, and subjective questionnaires were applied. Overall gustatory function based on the taste strip test was significantly decreased in patients with AD compared with controls in two out of three papers. The overall gustatory function of patients with AD was significantly decreased in all studies based on the taste disk and taste solution tests. We also found that the sweet taste test showed low heterogeneity across all the included studies, and there was low publication bias. In studies using subjective questionnaires, gustatory function was not significantly different between patients with AD and healthy controls in the meta-analysis. CONCLUSIONS: Based on these studies, gustatory dysfunction diagnosed by gustatory function testing was closely related to AD. However, the results of subjective questionnaires were not significantly different between patients with AD and healthy controls in the current meta-analysis. As the number of studies and enrolled subjects was limited and unified gustatory function testing was lacking, further studies are needed to confirm this relationship.

Effect of hyperbaric oxygen therapy on diabetes-related oral complications.

Background: Diabetes Mellitus is a chronic disease characterized by uncontrolled blood sugar levels, which lead to end-organ damage. While the diagnosis and treatment of its complications have been extensively studied, the effect of Hyperbaric Oxygen Therapy (HBO2) on diabetes-related oral complications remains unexplored. Aim: This prospective clinical study aims to investigate the effect of HBO2 on diabetes-related oral complications. Methods: Twenty patients diagnosed with diabetic foot ulcers and scheduled for HBO2 were included in this study. We recorded stimulated and unstimulated saliva pH, buffering capacity, flow rate, and subjective symptoms such as dry mouth, halitosis, taste loss, difficulty swallowing, and clinical examination findings before HBO2 and after the 21st session. Results: Upon comparing the findings, we observed a significant decrease in dry mouth and halitosis, periodontal disease severity, and healing of candida-related stomatitis and angular cheilitis. Despite not reaching statistical significance for other saliva parameters, the unstimulated salivary flow rate increased to normal limits (0.3-0.4 ml/min) in 6 out of 8 patients with a flow rate of less than 0.25 ml/min. Conclusion: Our study investigated the effect of HBO2 on diabetes-related oral complications for the first time, highlighting symptomatic relief for dry mouth and halitosis. Although our results are insufficient to report a definitive benefit, they underscore the need for further research on the oral health effects of HBO2.

Post-marketing surveillance of zinc acetate dihydrate for hypozincemia in Japan.

Zinc is an essential microelement, and its deficit causes various diseases and symptoms. In adults, especially in elderly individuals, zinc shortage can cause symptoms such as taste disorder, dermatitis, and susceptibility to infection. In children, zinc deficiency can lead to growth retardation. In 2017, the indication for zinc acetate dihydrate (NOBELZIN®) was expanded from Wilson's disease to include hypozincemia, leading to wider use of zinc acetate dihydrate. At five years after this broadening of use, we conducted a post-marketing study (PMS) to investigate the utilization, safety, and effectiveness of zinc acetate dihydrate. Over 52 weeks, the overall incidence of adverse drug reactions (ADRs) was 9.4% (87/928). The most common ADR was copper deficiency (2.4%), followed by nausea (1.4%). Among 928 patients, 19 (2%) developed serious ADRs. Of the patients with copper deficiency, 92% were >65 years of age, and all had comorbidities at baseline. Physicians evaluated the effectiveness of zinc acetate dihydrate using three categories: "effective", "not effective", and "indeterminate". The overall efficacy rate was 83.0%. The average serum zinc levels were elevated from 50-60 µg/dL to >90 µg/dL within 12 weeks, and were maintained up to 52 weeks after administration. Among the symptomatic sub-categories, the efficacy rate was highest in pressure ulcer (96.2%; 25/26), followed by in stomatitis (87.5%; 42/48), and taste disorder (87.4%; 181/207). Among pediatric patients with developmental symptoms, an efficacy rate of 66% was achieved. In conclusion, zinc acetate dihydrate has been safely used, and has produced beneficial effects on various diseases and symptoms.

Factors associated with impaired psychophysical gustatory function.

OBJECTIVE: To investigate the clinical characteristics associated with measured gustatory dysfunction in patients with chemosensory (smell and taste) discomfort. STUDY DESIGN: Retrospective study. DESIGN: Hospital-based cohort. SETTING: The clinical characteristics associated with the measured diagnosis of gustatory dysfunction were statistically analysed. PARTICIPANTS: Patients who underwent all the psychophysical olfactory and chemical gustatory function tests (YSK olfactory function test and chemical gustometry exam) and the subjective questionnaires between October 2021 and February 2023. MAIN OUTCOME MEASURES: YSK olfactory function test and chemical gustometry results, subjective questionnaire score about chemosensory (smell and taste) functions. The Medical records of patients who visited the smell and taste centre in a tertiary. RESULTS: A total of 219 patients were enrolled; 180 were diagnosed as having normal gustatory function, and 39 were diagnosed as having gustatory dysfunction. Subjective recognition of gustatory function was not associated with the measured gustatory function. Age, sex, measured olfactory function and the threshold and discrimination scores for the olfactory function test were significant factors in the multivariate analysis. When the patients were further divided according to age, the threshold test scores rather than other subsets in the olfactory function test were significantly associated with measured gustatory dysfunction in patients 60 and older. CONCLUSION: In older adult male patients with olfactory dysfunction, gustatory function should be considered regardless of subjective gustatory dysfunction.

Taste loss as a distinct symptom of COVID-19: a systematic review and meta-analysis.

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19 taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 235 meeting all inclusion criteria. Drawing on previous studies and guided by early meta-analyses, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct measures of taste are at least as sensitive as those obtained by self-report and that the preponderance of evidence confirms taste loss is a symptom of COVID-19. The meta-analysis showed that, among 138,015 COVID-19-positive patients, 36.62% reported taste dysfunction (95% confidence interval: 33.02%-40.39%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 15) versus self-report (n = 220) methodologies (Q = 1.73, df = 1, P = 0.1889). Generally, males reported lower rates of taste loss than did females, and taste loss was highest among middle-aged adults. Thus, taste loss is likely a bona fide symptom of COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

A quick test to objectify smell and taste dysfunction at home: a proof of concept for the validation of the chemosensory perception test.

Recent studies have shown the efficacy of a home test for the self-evaluation of olfactory and gustatory functions in quarantined coronavirus disease-2019 (COVID-19) patients. However, testing was often limited to COVID-19 participants, and the accuracy of home test kits was rarely compared to standardized testing. This study aims at providing proof of concept for the validation of the new Chemosensory Perception Test (CPT) developed to remotely assess orthonasal olfactory, retronasal olfactory, and gustatory functions in various populations using common North American household items. In the 2 experiments, a total of 121 participants irrespective of having olfactory and/or gustatory complaints from various causes (COVID-19, sinunasal, post-viral, idiopathic) were tested first, with one or many of the following tests: (i) a brief chemosensory questionnaire, (ii) an olfactory test-Sniffin' Sticks Test (SST) or University of Pennsylvania Smell Identification Test (UPSIT), and/or (iii) a gustatory test-Brief Waterless Empirical Taste Test (B-WETT). We then applied the CPT which yielded 3 different subscores, namely orthonasal, retronasal, and gustatory CPT scores. The orthonasal CPT score was significantly correlated with SST (ρ = 0.837, P < 0.001) and UPSIT (ρ = 0.364, P < 0.001) scores, and exhibited an excellent accuracy to identify olfactory dysfunction (OD) as compared to SST (area under the curve [AUC]: 0.923 [95% confidence interval {CI}, 0.822-1.000], P < 0.001). The retronasal CPT score but not the gustatory CPT score allowed to distinguish between participants with or without subjective gustatory complaint (AUC: 0.818 [95% CI, 0.726-0.909], P < 0.001). The CPT has the ability to identify OD and to quantify subjective gustatory complaints.