Use of platelet-rich plasma for COVID-19-related olfactory loss: a randomized controlled trial.

INTRODUCTION: The current study evaluated the use of platelet-rich plasma (PRP), an autologous blood product with supraphysiologic concentrations of growth factors, in the treatment of prolonged coronavirus disease 2019 (COVID-19)-related smell loss. METHODS: This multi-institutional, randomized controlled trial recruited patients with COVID-19 who had objectively measured smell loss (University of Pennsylvania Smell Identification Test [UPSIT] ≤ 33) between 6 and 12 months. Patients were randomized to three intranasal injections of either PRP or sterile saline into their olfactory clefts. The primary outcome measure was change in Sniffin' Sticks score (threshold, discrimination, and identification [TDI]) from baseline. The secondary end point measures included responder rate (achievement of a clinically significant improvement, ≥5.5 points TDI), change in individual TDI olfaction scores, and change in subjective olfaction via a visual analog scale. RESULTS: A total of 35 patients were recruited and 26 completed the study. PRP treatment resulted in a 3.67-point (95% CI: 0.05-7.29, p = 0.047) greater improvement in olfaction compared with the placebo group at 3 months and a higher response rate (57.1% vs 8.3%, odds ratio 12.5 [95% exact bootstrap confidence interval, 2.2-116.7]). There was a greater improvement in smell discrimination following PRP treatment compared with placebo but no difference in smell identification or threshold. There was no difference in subjective scores between PRP and placebo. No adverse effects were reported. CONCLUSION: Olfactory function following COVID-19 can improve spontaneously after 6 months and can improve to a greater extent with PRP injection. These data build on the promise of PRP to be a safe potential treatment option for patients with COVID-19-related smell loss, and larger-powered studies will help further assess its efficacy.

Olfactory Cleft Length: A Possible Risk Factor for Persistent Post-COVID-19 Olfactory Dysfunction.

INTRODUCTION: To date, little is known about predisposing factors for persistent COVID-19-induced olfactory dysfunction (pCIOD). The objective was to determine whether olfactory cleft (OC) measurements associate with pCIOD risk. MATERIAL AND METHODS: Three subgroups were recruited: group A included patients with pCIOD, group B included patients without olfactory dysfunction following SARS-CoV-2 infection (ntCIOD), and group C consisted in controls without past history of SARS-CoV-2 infection (noCOVID-19). Olfactory perception threshold (OPT) and visual analog scale for olfactory impairment (VAS-olf) were obtained. OC measurements were obtained through computed tomography scans. Results were subsequently compared. RESULTS: A total of 55 patients with a mean age of 39 ± 10 years were included. OPT was significantly lower in pCIOD patients (group A: 4.2 ± 2.1 vs. group B: 12.3 ± 1.8 and group C: 12.2 ± 1.5, p < 0.001). VAS-olf was significantly higher in pCIOD (group A: 6 ± 2.6 vs. group B: 1.7 ± 1.6 and group C: 1.6 ± 1.5, p < 0.001). OC length was significantly higher in group A (42.8 ± 4.6) compared to group B (39.7 ± 3.4, p = 0.047) and C (39.8 ± 4, p = 0.037). The odd of pCIOD occurring after COVID-19 infection increased by 21% (95% CI [0.981, 1.495]) for a one unit (mm) increase in OC length. The odd of pCIOD occurring was 6.9 times higher when OC length >40 mm. CONCLUSION: Longer OC may be a predisposing factor for pCIOD. This study is expected to encourage further research on OC morphology and its impact on olfactory disorders.

Management of Post-Infectious Anosmia and Hyposmia: A Systematic Review.

BACKGROUND: Anosmia and hyposmia significantly affect patients' quality of life and have many etiologies, including trauma, inflammatory conditions including chronic rhinosinusitis, neoplasm, and viral infections, such as rhinovirus and SARS-CoV-2. OBJECTIVE: Our purpose was to establish whether a consensus exists regarding optimal management of olfactory dysfunction and to provide insight into the treatment of anosmia in the current climate of increased prevalence secondary to COVID-19. Thus, we aimed to systematically review the literature on the management of non-Chronic-rhinosinusitis- related anosmia/hyposmia. METHODS: PubMed, EMBASE, and Cochrane databases were searched for articles published since January 1990 using terms combined with Medical Subject Headings (MeSH). We included articles evaluating management of anosmia and hyposmia written in the English language, with original data, a minimum of 3 months of follow-up except for COVID-related studies, at least 2 patients, and well-defined and measurable outcomes. RESULTS: A total of 3013 unique titles were returned upon the initial search. Of these, 297 abstracts were examined, yielding 19 full texts meeting inclusion criteria (8 with level 1 evidence, 3 with level 2, 1 with level 3, and 7 with level 4). The studies included a total of 1522 subjects, with follow up ranging from 3 to 72 months, with an exception for COVID related studies. Endpoints were based on clinically significant improvements of olfactory functions as measured through validated smell tests. Treatments with the most robust data were intranasal corticosteroids and olfactory training. CONCLUSION: The literature on the treatment of anosmia and hyposmia includes randomized trials showing the efficacy of a few modalities. While further research is needed to expand therapeutic options for this debilitating condition, the current literature supports the use of olfactory training and topical corticosteroids.

Smell and Taste Loss Associated with COVID-19 Infection.

OBJECTIVE: The aim of this study was to quantify the impact of COVID-19 on olfactory and gustatory function in US adults. METHODS: From the 2021 Adult National Health Interview Survey, demographic and survey-specific module data concerning COVID-19 diagnoses, testing and disease severity, and data quantifying disturbances and eventual recovery of smell and taste were extracted. Sample weights were applied to obtain nationally representative statistics. The overall rate of COVID-19 infection was determined, and those diagnosed with COVID-19 were analyzed with respect to disease severity, smell and taste disturbance, and respective recoveries. RESULTS: In 2021, 35.8 million or 14% of the adult population (95% CI 13.5-14.7%; mean age, 43.9 years; 53.8% female) had been diagnosed with COVID-19. Among those, 60.5% (58.6-62.5%) and 58.2% (56.2-60.1%) reported accompanying losses  in smell or taste, respectively; there was a significant association between overall COVID-19 symptom severity and smell (p < 0.001) and taste disturbance (p < 0.001). Following infection, 72.2% (69.9-74.3%), 24.1% (22.2-26.2%), and 3.7% (3.0-4.6%) of the patients experienced complete, partial, and no smell recovery, respectively. Recovery rates for gustatory function paralleled olfaction, with 76.8% (74.6-78.9%), 20.6% (18.7-22.7%), and 2.6 (1.9-3.4%) reporting complete, partial, and no recovery of taste, respectively. When sensory disturbance was present, severity of overall symptomatology was negatively associated with smell and taste recovery (p < 0.001 for each). CONCLUSION: The majority of adults infected with COVID-19 in 2021 experienced olfactory or gustatory dysfunction with a non-negligible population reporting incomplete or no near-term sensory recovery. Our results are useful for providers counseling patients and suggest that interventions lessening overall COVID-19 symptom burden may prevent prolonged sensory dysfunction. LEVEL OF EVIDENCE: IV. Laryngoscope, 2023.

Diagnosis and Treatment Strategy of Nasogenic Olfactory Dysfunction.

Since the global outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a symptom of the onset of SARS-CoV-2, olfactory dysfunction (OD), has attracted tremendous attention. OD is not only a negative factor for quality of life but also an independent hazard and early biomarker for various diseases, such as Parkinson's and Huntington's diseases. Therefore, early identification and treatment of OD in patients are critical. Many etiological factors are responsible for OD based on current opinions. Sniffin'Sticks are recommended to identify the initial position (central or peripheral) for OD when treating patients clinically. It is worth emphasizing that the olfactory region in nasal cavity is recognized as the primary and critical olfactory receptor. Many nasal diseases, such as those with traumatic, obstructive and inflammatory causes, can lead to OD. The key question is no refined diagnosis or treatment strategy for nasogenic OD currently. This study summarizes the differences in medical history, symptoms, auxiliary examination, treatment and prognosis of different types of nasogenic OD by analyzing the current studies. We propose using olfactory training after 4-6 weeks of initial treatment for nasogenic OD patients with no significant improvement in olfaction. We hope that our research can provide valuable clinical guidance by systematically summarizing the clinical characteristics of nasogenic OD.

Omega-3 Fatty Acid Supplementation for the Treatment of Persistent COVID-Related Olfactory Dysfunction.

OBJECTIVE: To evaluate the efficacy of omega-3 fatty acid (O3FA) supplementation in the treatment of COVID-related olfactory dysfunction (OD). METHODS: Patients with laboratory-confirmed or clinically-suspected COVID-19 infection and new-onset OD from August 2020 to November 2021 were prospectively recruited. Patients with quantitative OD, defined as a brief smell identification test (BSIT) score of 9 or less, were eligible for study inclusion. The experimental group received 2 g of O3FA supplementation, while the control group received an identical placebo to be taken daily for 6 weeks. The primary outcome was a change in BSIT score between the initial and 6-week follow-up tests. RESULTS: One hundred and seventeen patients were included in the analysis, including 57 patients in the O3FA group and 60 in the placebo group. O3FA group patients demonstrated a mean BSIT improvement of 1.12 ± 1.99 compared to 0.68 ± 1.86 in the placebo group (p = 0.221). Seventy-seven patients, 42 within the O3FA group and 35 in the placebo group, completed a follow-up BSIT survey at an average of 717.8 days from study onset. At long-term follow-up, there was an average BSIT score improvement of 1.72 within the O3FA group compared to 1.76 within the placebo group (p = 0.948). CONCLUSION: Among patients with persistent COVID-related OD, our study showed no clear evidence of relative short-term or long-term olfactory recovery among patients receiving high doses of O3FA supplementation.

Recovery from olfactory and gustatory dysfunction following COVID-19 acquired during Omicron BA.1 wave in Italy.

BACKGROUND: Despite alterations in the sense of smell and taste have dominated the symptoms of SARS-CoV-2 infection, the prevalence and the severity of self-reporting COVID-19 associated olfactory and gustatory dysfunction has dropped significantly with the advent of the Omicron BA.1 subvariant. However, data on the evolution of Omicron-related chemosensory impairment are still lacking. OBJECTIVE: The aim of the present study was to estimate the prevalence and the recovery rate of self-reported chemosensory dysfunction 6-month after SARS-CoV-2 infection acquired during the predominance of the Omicron BA.1 subvariant in Italy. METHODS: Prospective observational study based on the sino-nasal outcome tool 22 (SNOT-22), item "sense of smell or taste" and additional outcomes conducted in University hospitals and tertiary referral centers in Italy. RESULTS: Of 338 patients with mild-to-moderate COVID-19 completing the baseline survey, 294 (87.0 %) responded to the 6-month follow-up interview. Among them, 101 (34.4 %) and 4 (1.4 %) reported an altered sense of smell or taste at baseline and at 6 months, respectively. Among the 101 patients with COVID-19-associated smell or taste dysfunction during the acute phase of the disease, 97 (96.0 %) reported complete resolution at 6 months. The duration of smell or taste impairment was significantly shorter in vaccinated patients (p = 0.007). CONCLUSIONS: Compared with that observed in subjects infected during the first wave of the pandemic, the recovery rate from chemosensory dysfunctions reported in the present series of patients infected during the predominance of the Omicron BA.1 subvariant was more favorable with a shorter duration being positively influenced by vaccination.

COVID-19 olfactory dysfunction, evaluation of onset, and persistence.

Olfactory dysfunction (OD) is a common feature of COVID-19. The goal of the study was to define the modes of onset of OD in the clinical course of the disease and to follow the cases for 12-18 months in order to estimate the differences in the recovery time from OD over the course of the disease. We managed to follow a total of 325 patients (females: 198, males: 127) in the Babylon governorate in Iraq. All were COVID-19 patients who should have OD during the course of the disease. COVID-19 infection was established in all patients by swab test, i.e. polymerase chain reaction (PCR) and/or chest computed tomography findings of pneumonia compatible with COVID-19. Detailed medical records were obtained directly from the patients or their relatives. The patients were then followed up by telephone and questioned with structured questionnaires concentrating upon general clinical features and the sense of olfaction. Information about the presence of olfactory disorders, their occurrence, and development was recorded. Based on the onset of OD, the patients were categorized into three groups. Olfactory functions were assessed primarily by face-to-face interview and then (if necessary) by a telephone questionnaire assessing self-reported olfactory function and olfactory-related quality of life, which measures the subjective olfactory capability (SOC). In the first 2 weeks, 148 (45.5%) patients reported complete recovery from OD, of which 90 (73.2%) patients joined at the end of the 1st month. OD persistence was observed in 11 (3.3%) patients toward the end of the 1st year, in 5 (1.5%) patients at the end of the 15th month, and only in two (0.6%) patients at the end of the 18th month. We found no significant correlation between the type of onset of OD and the duration and persistence of OD. Most sufferers of COVID-associated OD recover their sense of smell within the 1st month.

The Retrospective Pilot Study of the Prevalence of Olfactory Dysfunction or Loss of Smell, Loss of Taste and Oral Manifestations Among COVID-19 Positive Health Workers in Muscat, Oman.

A retrospective study evaluating the prevalence of loss of smell, loss of taste and oral manifestations was carried out by framing an online questionnaire and disseminated among the health care workers including medical and dental students, who were afflicted with COVID-19. The objective of this study was to find out the prevalence of the loss of smell, loss of taste (LOST) and oral manifestations and whether these (LOST & oral manifestations) can be the premonitory manifestations and also whether these can predict the prognosis of COVID-19 disease. Our study showed that the loss of smell, loss of taste and dry mouth did occur before the other symptoms considerably in the COVID-19 infected health workers. All the infected health workers were in home quarantine phase and not hospitalized during the occurrence of COVID-19. The loss of smell, loss of taste and oral manifestations can be the prodromal signs of COVID-19 and may be used as a screening tool to predict the severity of the disease. Supplementary Information: The online version contains supplementary material available at 10.1007/s12070-022-03293-w.

Parosmia and altered taste in patients recovering from Covid 19.

Parosmia is a well-documented consequence of smell loss associated with Covid 19. Those who experience this qualitative olfactory disorder during recovery find that the odour of common foods and household items is distorted, and the experience can range from merely altered to profoundly disgusting. This can lead to a greatly altered relationship with food, including the physical symptoms of loss of appetite, nausea, vomiting, as well as wider reaching issues such as withdrawal from social situations, emotional distancing from others in their close social circles, and anhedonia. There is at present no known cure or intervention to mitigate the condition. The AbScent Parosmia and Phantosmia support group on Facebook became an important resource for patients with this condition during the early part of the pandemic, and the crowd-sourcing of experiences, tips and peer-to-peer advice became a valuable source of information for the community as well as researchers trying to understand the condition. Using protocols described in earlier literature on the use of social media for qualitative research, this paper provides information on the management of parosmia based on the experiences of over 30k patients in the AbScent Parosmia and Phantosmia group on Facebook and 6k member of the AbScent Network.

Anosmia-An Effect of COVID-19 Infection-Review.

The World Health Organization announced on March 11, 2020 that COVID-19 could become a pandemic. COVID-19 is a contagious disease caused by the coronavirus that causes severe acute respiratory syndrome (SARS-CoV-2). Viruses usually enter the body through the mouth or nose. The virus then enters the alveoli, which are small air sacs inside the lungs. Cough, fatigue, fever, shortness of breath or breathing difficulties, and loss of smell and taste are all symptoms of COVID-19. Anosmia, also known as smell blindness, is a condition in which the ability to detect one or more smells is lost. Olfaction uses chemoreceptors to create signals that are processed in the brain and form the sense of smell in anosmia. Anosmia is recognised as a COVID-19 symptom in many countries, and some have developed "smell tests" as potential screening tools. The first level of screening, which is currently used in India, is primarily based on temperature and can result in false positives and negatives (fever as a symptom has not yet been developed although infection). One of the methods for detecting COVID-19 is an intermediate level of screening based on assessing an olfactory function, depending on the usage. This paper provides an overview of COVID-19 and its effects on the human body, as well as an overview of anosmia and how it contributes to one of the symptoms of COVID-19.

The potential therapeutic effect of platelet-rich plasma in the treatment of post-COVID-19 parosmia

Background: COVID-19-related olfactory dysfunction is an emerging problem with a significant impact on the quality of life of affected individuals. Different lines of treatment have been used with varying results. This study aimed to assess the potential therapeutic effect of PRP in the treatment of post-COVID olfactory dysfunction. This work aimed to assess the potential therapeutic effect of platelet-rich plasma (PRP) in treating post-COVID-19 parosmia. A pilot study was conducted on 60 patients with post-COVID parosmia without responding to a 3-month course of olfactory training, topical corticosteroids, omega-three, vitamin B12, and zinc supplementation. The patients were distributed randomly and equally among 2 groups. The case group was subjected to three PRP injections in the olfactory cleft at 3 weeks intervals. The control group continued the pre-study treatment protocol for 6 weeks. The degree of parosmia was assessed before and after treatment subjectively using a visual analog scale (VAS) from 0 to 10. Reaching 0-1 on the visual analog scale was a complete improvement. The primary outcome was assessing the post-treatment score for parosmia 1 month after the third injection in the case group. The second outcome was the comparison between both groups regarding the degree of improvement 1 month after cessation of treatment. Result(s): There was a highly significant improvement in VAS for parosmia (p < 0.00001) in the case group and a significant improvement in VAS for parosmia in the control group (p = P = 0.00148). There was a significant difference between both groups regarding the degree of improvement favoring the case group (p = 0.002). Conclusion(s): Platelet-rich plasma injection in the olfactory cleft offers a therapeutic option for treating patients with post-COVID-19 olfactory parosmia who failed to respond to traditional conservative treatment.Copyright © 2022, The Author(s).

Olfactory dysfunction in patients with Wilson's Disease.

INTRODUCTION: Many neurodegenerative disorders are associated with olfactory dysfunction (OD), but little is known about OD in Wilson's Disease (WD). We evaluated olfactory function in patients with WD. MATERIAL AND METHODS: OD was examined in 68 patients with WD and 70 sex- and age-matched healthy controls using subjective testing with 'Sniffin Sticks'. Threshold discrimination identification (TDI) score and its three components (odour detection threshold, discrimination, and identification) were assessed. RESULTS: Compared to controls, patients with WD had a significantly weaker sense of smell in terms of TDI (p < 0.01), odour discrimination (p < 0.01), and identification (p < 0.01), but not in terms of odour detection threshold (p = 0.27). Patients with predominantly neurological symptoms were characterised by greater OD by TDI (p < 0.01), odour detection threshold (p = 0.01), and discrimination (p = 0.03). The presence of pathological lesions (p = 0.04) in brain magnetic resonance imaging and generalised brain atrophy (p = 0.02) predisposed to worse TDI. In the WD group, weak inverse correlations between age and TDI score (r = -0.27), odour detection threshold (r = -0.3), and discrimination (r = -0.3) were found. Male gender was a risk factor for abnormal TDI in both WD and controls (both p = 0.02). CONCLUSIONS: Patients with WD, particularly older individuals, more frequently had OD than healthy volunteers. Predominantly neurological symptoms, and the presence of typical brain MRI changes, predisposed patients with WD to smell disorders.

Is Olfactory Testing a Useful Diagnostic Tool to Identify SARS-CoV-2 Infections Early? A Cross-Sectional and Longitudinal Analysis.

BACKGROUND: Genesis and the prognostic value of olfactory dysfunction (OD) in COVID-19 remain partially described. The objective of our study was to characterize OD during SARS-CoV-2 infection and to examine whether testing of OD may be a useful tool in clinical practice in order to early identify patients with SARS-CoV-2 infection. METHODS: Olfactory function assessment was objectively carried out using the u-Smell-it® test. In a cross-sectional study part, we evaluated this test in a control cohort of SARS-CoV-2 negative tested patients, who attended the University Hospital Frankfurt between May 2021 and March 2022. In a second longitudinal study part, sensitivity and specificity of OD was evaluated as a diagnostic marker of a SARS-CoV-2 infection in Frankfurt am Main, Germany in SARS-CoV-2 infected patients and their close contacts. RESULTS: Among 494 SARS-CoV-2 negative tested patients, OD was detected in 45.7% and was found to be significantly associated with the male gender (p < 0.001), higher age (p < 0.001), cardiovascular and pulmonary comorbidities (p < 0.001; p = 0.03). Among 90 COVID-19 positive patients, OD was found in 65.6% and was significantly associated with male gender and positive smoking status (p = 0.04 each). Prevalence and severity of OD were significantly increased in infections with the Delta variant (B.1.617.2) compared to those with the Omicron variant (BA.1.1.529). Diagnostic sensitivity and specificity of OD for diagnosis of SARS-CoV-2 infection were 69% and 64%, respectively. CONCLUSION: OD is common in COVID-19 negative and positive tested patients with significantly different prevalence rates observed between different variants. Diagnostic accuracy of OD is not high enough to implement olfactory testing as a tool in diagnostic routine to early identify patients with a SARS-CoV-2 infection.

Olfactory and Taste Dysfunction in Indian Population with COVID-19: A Study on 300 Patients.

The novel coronavirus disease 2019 is an ongoing pandemic and a global health emergency. Since the main portal of entry for the virus is the nose, olfactory and taste dysfunction have gained attention as important symptoms in COVID-19. The primary objectives are to assess the prevalence of olfactory and taste dysfunction in patients affected with COVID-19. And to determine whether anosmia and ageusia are early predictors of COVID-19. A prospective study was conducted on 300 patients who were laboratory diagnosed cases of COVID-19 admitted in tertiary care centre and a covid care centre. A written informed consent was taken. All patients underwent olfactory and taste examination and the details were noted in a case-record proforma. The prevalence of olfactory dysfunction in COVID-19 patients was 21% and that of taste dysfunction was 26.6%. Majority of the affected individuals were males and mainly of the younger age group. These symptoms lasted for a duration of 7-9 days and 97% of the patients showed complete recovery. Acute sudden onset olfactory and taste dysfunction seems to be a useful indicator for early diagnosis of patients thus helping in early isolation, timely management of the illness and controlling the spread of the disease.

Olfactory and Taste Dysfunction in Coronavirus Disease 2019 Pandemic.

This study is done to raise awareness of olfactory and taste dysfunction association in coronavirus disease, urging early detection and isolation of coronavirus positive patients thus breaking the chain of transmission of disease. This is a retrospective observational study done in outpatient department of tertiary care hospital in Mumbai, west India from 1st May 2020 to 1st August 2020 on patients who were confirmed positive for COVID-19 by real-time reverse transcription polymerase chain reaction (rRT-PCR) and having olfactory dysfunction and/or taste disorders. In study population, anosmia and ageusia occurred in 88% and 83.33% respectively. In control population, anosmia and ageusia occurred in 93% and 85.71% respectively. The mean duration of anosmia was around 2 weeks and 3 weeks for study and control group respectively. In study population 94.6% recovered from anosmia, whereas in control population 64.3% recovered from anosmia. Anosmia gradually improved to hyposmia. In the study population 94.3% hyposmia patients showed recovery, while in control population 85.2% showed recovery. Ageusia collaborated with the duration of anosmia. Recovery from taste dysfunction was 88.6% and 63.9% in study and control population respectively. Olfactory and taste dysfunction are very important clinical features of coronavirus positive patients with anosmia being the most prominent symptom. All patients presenting with smell and or taste dysfunction should be screened for coronavirus disease, helping in early detection in asymptomatic patients.

Prevalence of Olfactory Dysfuntion in SARS-COV-2 Positive Patients.

Severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) is associated with chemosensory symptoms including olfactory dysfunction and dysgeusia. Multiple studies have reported differing prevalence rates of symptoms and recovery rates depending on geographic location. The purpose of the study was to determine the prevalence and features of Covid19 olfactory dysfunction in a developing nation. We conducted a prospective study at a tertiary, high-volume centre in South Africa, to determine the prevalence of olfactory dysfunction in SARS-COV-2 positive patients. The average recovery time of the olfactory dysfunction was also evaluated. The study included patients diagnosed with SARS-COV-2 infection between November 2020 and January 2021. Patients were recruited to participate in a survey which assessed demographic data, date of diagnosis, initial symptoms, presence and recovery time of olfactory dysfunction symptoms. A total of 86 patients with olfactory dysfunction were included and followed up telephonically over 6 weeks in 2 week intervals to determine recovery time. There was a prevalence rate of 40.7% of olfactory dysfunction in patients in our study. A higher proportion of patients with olfactory dysfunction had fever compared to those without and this was a significant finding in our study population. The overall median recovery time in our study was 7 days. Prevalence of olfactory dysfunction in our population is in keeping with European studies and most patients recover their sense of smell within a week.

Disorders of smell and taste in COVID-19

Loss of smell is one of the symptoms most frequently reported by patients with COVID-19. Although the spontaneous cure rate is high, recent studies have shown that up to 7% of patients remain anosmic for more than 12 months after the onset of infection, leaving millions of people worldwide with severe olfactory dysfunction. Smell training is still the first recommended form of treatment. In view of the continued lack of approved drug treatment options, new therapeutic options are being explored. This article provides an overview of the current state of science on COVID-19-related olfactory disorders, with a focus on epidemiology, pathophysiology, cure rates, currently available treatments, and research into new treatments.

Persistent olfactory dysfunction in mild COVID-19 patients: A descriptive study of the characteristics and association with other symptoms.

Introduction: Post-COVID olfactory dysfunction continues to be studied due to the controversy of the mechanisms involved. The aim was to investigate the olfactory dysfunctions in association with other post-COVID symptoms. Material and methods: Observational, descriptive and single-center study. The patients had confirmed mild COVID-19 and subjective olfactory dysfunction of more than a month of evolution, which was assessed by Sniffin' Sticks Olfactory Test. Results: A total of 86 patients participated. The mean age was 37.2 years (SD 9.82). 70.9% reported parosmia and 46.5% symptoms of brain fog. A pathological test result was obtained in 72.1% of the participants. The most failed pen was 11 (apple) in 76.7%. Anosmia of pen 15 (anise) was reported more frequently in 24.4% and cacosmia of pen 9 (garlic) in 27.9%. We observed a significant association between patients who reported parosmias and brain fog (RR 2.18; p = 0.018), also between parosmia and phantosmia (RR 6.042; p < 0.001). Conclusion: There is some pathological selectivity for certain test pens, a higher prevalence of cognitive symptoms and many patients with combined parosmia and brain fog.

Introducción: La alteración olfatoria post-COVID continúa en estudio por la controversia sobre los mecanismos implicados. El objetivo de este estudio es caracterizar las alteraciones olfatorias y su relación con otros síntomas post-COVID. Material y métodos: Estudio unicéntrico, observacional y descriptivo. Los pacientes tuvieron infección por COVID-19 leve confirmada y disfunción olfatoria subjetiva de más de un mes de evolución, evaluada con el Sniffin' Sticks Olfatory Test. Resultados: Se seleccionaron 86 pacientes. La edad media fue de 37,2 años (DE 9,82). El 70,9% refirieron parosmia y el 46,5% niebla mental. Se obtuvo un test patológico en el 72,1% de los participantes. El lápiz más fallado fue el número 11 (manzana), en el 76,7%. La anosmia fue reportada más frecuentemente con el lápiz 15 (anís) y la cacosmia con el lápiz 9 (ajo) en el 27,9%. Observamos una asociación significativa entre pacientes que refieren parosmias y niebla mental (RR 2,18; p = 0,018) y entre parosmia y fantosmia (RR 6,042; p < 0,001). Conclusión: Se observa anosmia y cacosmia selectiva para algunos olores testados. Hay una alta prevalencia de síntomas cognitivos, más frecuentes en pacientes con parosmia.