|Year : 2021 | Volume
| Issue : 2 | Page : 196-201
Olfactory and Taste Dysfunction and Its Correlation with Viral Load on Reverse Transcription-Polymerase Chain Reaction among COVID-19 Patients: A Comparative Study from Tribal India
Izhar Khan1, Vikas Gupta2, Abhishek Gaur3, Sanjay Kumar Shukla1, Shewtank Goel3
1 Department of Otorhinolaryngology, Government Medical College, Shahdol, Madhya Pradesh, India
2 Department of Community Medicine, Government Medical College, Shahdol, Madhya Pradesh, India
3 Department of Microbiology, Government Medical College, Shahdol, Madhya Pradesh, India
|Date of Submission||24-Jul-2021|
|Date of Decision||18-Aug-2021|
|Date of Acceptance||04-Sep-2021|
|Date of Web Publication||29-Dec-2021|
Dr. Vikas Gupta
Department of Community Medicine, Government Medical College, Shahdol, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
Background and Aim: Coronavirus disease-19 (COVID-19) diagnosis is confirmed by detection of viral nucleic acid by reverse transcription-polymerase chain reaction (RT-PCR), in the upper respiratory samples through nasopharyngeal or oropharyngeal swabs or sputum. The present study compared the means of viral load on RT-PCR among COVID-19 patients with and without olfactory and taste dysfunction (OTD) admitted to dedicate COVID-19 hospital (DCH). Materials and Methods: This cross-sectional comparative study was conducted after IEC approval in DCH Shahdol for a period of 4 months, and RT-PCR positive patients were divided into two groups, Group A (with OTD) and Group B (with no OTD) using chemosensitive psychophysical test. The sample size was calculated as 160 (Group A = 80 and Group B = 80) by using sample size formula: (σ21+ σ22/K) (z1− α/2 + z1− β)2/Δ2. During data analysis, an association was significant for P < 0.05. Results: Among total subjects (n = 160), 129 subjects reported the history of fever or malaise followed by cough among 55 subjects. It was observed that from Group A and Group B, 38.7% and 36.2% of subjects stayed in hospital for <5 days, respectively. The differences in the mean Ct values, of all the three genes, between Group A and Group B were found to be statistically significant (P < 0.05). Conclusion: The loss of smell and taste are important symptoms in COVID-19 patients. It need to be carefully assessed even in asymptomatic patients to reduce the further transmission of the virus in the community. This may help in further reducing the transmission of the virus in the community.
Keywords: Ageusia, anosmia, chemosensory loss, cycle threshold value, nasopharyngeal swab
|How to cite this article:|
Khan I, Gupta V, Gaur A, Shukla SK, Goel S. Olfactory and Taste Dysfunction and Its Correlation with Viral Load on Reverse Transcription-Polymerase Chain Reaction among COVID-19 Patients: A Comparative Study from Tribal India. Arch Med Health Sci 2021;9:196-201
|How to cite this URL:|
Khan I, Gupta V, Gaur A, Shukla SK, Goel S. Olfactory and Taste Dysfunction and Its Correlation with Viral Load on Reverse Transcription-Polymerase Chain Reaction among COVID-19 Patients: A Comparative Study from Tribal India. Arch Med Health Sci [serial online] 2021 [cited 2022 Oct 1];9:196-201. Available from: https://www.amhsjournal.org/text.asp?2021/9/2/196/334005
| Introduction|| |
An unprecedented disease hit the world some time ago. The World Health Organization declared this a coronavirus disease-19 (COVID-19) pandemic on March 11, 2020. It has affected over 103,989,900 and killed 2260,259 people by February 05, 2021, with patients suffering from the COVID-19, presenting with a wide array of symptoms ranging from fever and respiratory distress to gastrointestinal symptoms. The death count has been rapidly rising though the level (5.6%) has not reached the infliction by the other members of the coronavirus family causing human illnesses such SARS (13%) and MERS (35%).
However, COVID is far more transmissible with an estimated reproduction number (R0) 3.32. India too now is in the grip of the pandemic and, in terms of absolute numbers, the second worst affected country after the USA. Early countrywide lockdown helped in delaying the spread and shift the peak and gave time to create infrastructure to face the surge. Despite this, a total of 10,790,183 cases and 154,703 deaths have been reported in India as of February 05, 2021.
Many professional organizations have now recognized olfactory and taste dysfunction (OTD) as symptoms of COVID-19 and included them in their diagnostic guidelines. There is a varying prevalence of OTD in COVID-19 patients, with a higher prevalence reported in the European population as compared to the Asian population. COVID-19 diagnosis is confirmed by detection of viral nucleic acid by RT-PCR, in the upper respiratory samples through nasopharyngeal or oropharyngeal swabs or sputum.
Real-time reverse transcription PCR yields cycle threshold (Ct) value (Ct value), which is defined as the number of amplification cycles required to reach a threshold for detection of the viral nucleic acid. Ct value is inversely proportional to the amount of target nucleic acid in the sample, i.e. lower the Ct value, greater the amount of target nucleic acid in the sample.
The association between Ct values and disease severity of COVID-19 is still controversial. However, there is limited data comparing the Ct values with chemosensory loss. The present study compared the means of viral load on RT-PCR among COVID-19 patients with and without OTD admitted to dedicate COVID-19 hospital (DCH). This will help in triaging the rapid rise of patients and streamlining resources for better management of cases with optimal efficiency and better outcomes for the future upcoming third COVID-19 wave. This may help in further reducing the transmission of the virus in the community.
| Materials and Methods|| |
Study setting and design
This cross-sectional comparative study was conducted in DCH at Government Medical College, Shahdol, Madhya Pradesh, India, for a period of 4 months (March 2021 to June 2021). GMC Shahdol was recognized as official sites as DCH for managing COVID-19 patients on March 27, 2020, when the disease started to occur in the epidemic proportion in India.
Study population and sample size
The study subjects were the patients (18 years or above) tested positive (Ct value <35 was considered as COVID-19 positive) for COVID-19 infection by RT-PCR based test with mild, moderate, and severe disease admitted to DCH that is designated as COVID-19 hospitals by the State Government. The study did not include children (<18 years of age), patients with psychiatric or neurological disorders, patients with a history of previous surgery or radiation in the oral and nasal cavities, chronic rhinosinusitis, and preexisting smell and taste disturbances.
The RT-PCR positive patients were divided into two groups: Group A and Group B. Group A included patients with OTD and Group B included patients with no OTD. The sample size was calculated as 160 (Group A = 80 and Group B = 80) considering the mean Ct for E Gene of Group A as 24.43 ± 6.70 and of Group B as 27.39 ± 7.92 with confidence level of 95%, 5% absolute allowable error, and 80% power by using sample size formula:
k = n2/n1 = 1, n1= (σ21+ σ22/K) (z1− α/2 + z1− β)2/Δ2, n1= (6.72 + 6.72/1)(1.96 + 0.84)2/2.962, n1 = 80, n2 = K * n1 = 80.
where Δ = | μ2− μ1 | = Absolute difference between two means (Group A and Group B); σ1, σ2 = Variance of mean (Group A and Group B); n1, n2 = Sample size (Group A and Group B); α = Probability of Type I error (usually 0.05); β = Probability of Type II error (usually 0.2); z = Critical Z value for a given α or β; k = Ratio of sample size for Group B to Group A. Hence, eligible study participants (n = 160) were included in the study using convenient sampling method [Figure 1].
The chemosensitive psychophysical test procedure was applied objectively to identify the subjects for Group A and Group B. The test methodology and the scoring system were adapted from the studies conducted by Vaira et al.
Sampling collection and laboratory procedure
Nasopharyngeal swab for RT-PCR was taken from enrolled subjects at the time of presentation. The nasopharyngeal swab was transported in viral transport medium (VTM) in a triple-layered packaging in an ice box from the sample collection site to the college microbiology laboratory. RNA was extracted from 150 μL of VTM using viral RNA isolation kit and was eluted in 50 μL of nuclease-free water and used as a template for quantification of SARS-CoV-2 viral RNA levels by RT-PCR. The COVID-19 test by RT-PCR was done, with 3 gene detections: E (Envelope encoding) gene, N (nucleocapsid encoding) gene, and RdRp (RNA-dependent RNA polymerase) gene. Ct value of each of the three genes was compared between Groups A and B.
Participation in this survey was voluntary and was not compensated. After obtaining approval to conduct study from the Institutional Review Board (IERB), the admitted COVID-19 patients were approached with an introductory paragraph outlining the aims and objectives of the study. Informed consent was obtained from eligible subjects before participation. The demographic details (age and gender) and detailed clinical history (symptoms, comorbidities, admitted to HDU/isolation/ICU) of the patient were taken. The chemosensitive psychophysical test procedure was explained to the subjects, and both the olfactory and gustatory functions were objectively evaluated during ENT consultation. All the patients were followed up till RT-PCR test was reported negative. The information pertaining to subjects was kept anonymous and confidential.
Collected data was entered in the MS Excel spreadsheet, was coded appropriately, and was later cleaned for any possible errors. Analysis was carried out using IBM SPSS Statistics for Windows, Version 22.0 (IBM Corp. Armonk, NY, USA). During data cleaning, to facilitate association of variables, more variables were created. Clear values for various outcomes were determined before running frequency tests. Categorical data was presented as percentages (%) and quantitative data was presented as mean (standard deviation). Chi-square was used as test of significance to observe the difference between categorical variable in two groups (Groups A and B) and for continuous variables, independent 't' test was used. All tests (two tailed) were performed at a 5% level of significance; thus, an association was significant if P < 0.05.
All ethical issues were followed during the study. Participation was voluntary and participants were allowed to withdraw from study at any moment. No personal data was recorded. Participants were assured that all data collected was used only for the current study. Study was initiated after approval from IERB (Project ID: IERC/21/03/004). In addition, before filling the questionnaire, participants were asked to give their consent to participate in the study.
| Results|| |
The present study included 160 subjects, 80 in each Group A and Group B. The mean age of the study subjects from Group A was 35.8 ± 14.6 and for Group B, the mean age of subjects was 34.8 ± 13.7. As shown in [Table 1], there was no statistically significant difference between the Group A and Group B for the given age groups. The subjects admitted to hospital were mostly males (55.0%, 88/160). The comorbid conditions such as hypertension, diabetes mellitus, asthma, COPD, and others were reported among nearly one third of subjects (29.4%, 47/160). The history of alcohol intake, smoking, or tobacco chewing was observed among two fifth of admitted subjects (21.3, 34/160).
|Table 1: Baseline characteristics of study subjects (Group A and Group B)|
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[Table 2] shows that in Group A, 60.0% subjects got admitted to hospital within 5 days of onset of symptoms whereas for Group B, 71.3% of subjects got admitted to hospital within 5 days of onset of symptoms. Among total subjects (n = 160), 129 subjects reported the history of fever or malaise followed by cough among 55 subjects. Only 5.6% of subjects (9/160) required mechanical ventilation as O2 support. It was observed that from Group A and Group B, 38.7% (31/160) and 36.2% (29/160) of study subjects stayed in hospital for <5 days, respectively. The Chi-square analysis for different variables reflected no statistically significant difference (P > 0.05) between Group A and Group B except for the variable “days from onset of symptoms to admission” (P < 0.05).
|Table 2: Clinical characteristics of study subjects (Group A and Group B)|
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[Table 3] shows the mean Ct values of the three genes N gene, E gene, and RdRp gene, of Group A and Group B. The differences in the mean Ct values, of all the three genes, between Group A and Group B were found to be statistically significant (P < 0.05).
|Table 3: Comparison of cycle threshold values (mean) for 3 genes between the Group A and Group B|
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| Discussion|| |
Sudden onset loss of smell and taste is now well-documented symptoms of COVID-19 and has now been incorporated in various diagnostic guidelines. Its prevalence varies between populations. Study from Luers et al. showed reduced olfaction occurred in 74% of COVID-19 patients while reduced a sense of taste was presented in 69% of COVID-19 patients. A study by Roland et al. showed that the smell or taste change is a strong predictor for a COVID-19-positive test result. Using the presence of smell or taste change with fever, this parsimonious classifier correctly predicts 75% of COVID-19 test results. Similarly, a study by De Maria et al. reflected that 50.5% of patients had extensive taste disorder and had an associated self-assessed olfactory dysfunction compared to their experience before onset of fever and COVID-19 symptoms. A meta-analysis of 10 large cohort studies of olfactory dysfunction and nine large cohort studies of gustatory dysfunction showed a prevalence of 52.5% and 43.93% of olfactory and gustatory dysfunction, respectively.
However, the pathophysiology mechanism of OTD in COVID-19 is still unknown. The most likely mechanism is that SARS-CoV-2 targets the angiotensin-converting enzyme 2 receptors found on the sustentacular and basal cells of the nasal epithelium, including the olfactory epithelium. It is also postulated that the virus invades the central nervous system through the olfactory bulb.
The diagnosis of COVID-19 requires detection of SARS-CoV2 RNA by RT-PCR on respiratory samples. Higher viral load has been detected in the nasopharynx than oropharynx. Therefore, in this study, nasopharyngeal swab was taken of all the patients. Quantitative RT-PCR provides real-time quantification by first transcribing SARS-CoV-2 RNA into DNA by reverse transcriptase. Then, quantitative PCR is performed wherein a fluorescence signal increases proportionally to the amount of amplified nucleic acid. This yields a Ct value that is inversely proportional to the amount of target virus in the sample. Therefore, Ct value may indicate the viral replication activity level and viral load. This may be helpful in isolating the patients with a higher viral load to reduce the transmission of the virus.
The correlation of COVID-19 symptoms and viral load remains controversial. Some studies indicate that a high viral load might be a risk factor for severe disease., Whereas, other studies did not observe any difference in the viral load between asymptomatic and symptomatic patients. These differences may be due to the variation in the study design, the type and timing of respiratory sampling, the method of taking the respiratory sample. In the present study, only nasopharyngeal swabs were collected for the patients at the time of consultation. Patients with mild, moderate, or severe diseases were included in the present study.
It is still unclear if viral load is associated with OTD. Hence, the present study was attempted to find the correlation between Ct value and OTD. In the present study, it was found that the Ct values of COVID-19 patients with OTD were significantly lower than the Ct values of the patients without OTD. This result suggests that COVID-19 patients with OTD had a higher viral load than those without OTD. This association of OTD with a higher viral load may be helpful in preventing the transmission of the virus.
Similar findings were observed in the study conducted by Nakagawara et al. which demonstrated that fever and OTDs were significantly associated with a higher viral burden and longer time to negative RT-PCR. But opposite to the present study, Biguenet et al. found that anosmia was significantly associated with a lower viral load, however, it could not be excluded that a delayed appearance of OTD symptoms during the course of the disease has allowed time for the viral load to decrease. Further, on the contrary, the studies by Cho et al. and Vaira et al. found no correlation between the Ct values of PCR for individual patients and the presence or absence of olfactory and gustatory dysfunction.,
The present study collected single type of respiratory samples (nasopharyngeal specimens) in a quite homogenous population (monocentric study from in our institution), it might be difficult to extrapolate the quantitative SARS-CoV-2 viral loads observed to other populations of patients and to other types of respiratory specimens. Hence, authors suggest upcoming studies to involve more than one center to enhance generalizability of the observations. However, apart from the limitations, the strengths of the present study are that the chemosensitive psychophysical test procedure was applied objectively to identify the subjects, so recall bias was completely removed. Furthermore, the present study included mild, moderate, and severe cases, so correlation with the Ct values of the PCR test for SARS-CoV-2 reflects the true situation of the COVID-19 pandemic in this tribal district.
| Conclusion|| |
The present study has further strengthened the evidence regarding correlation between Ct values and OTD. As loss of smell and taste are important symptoms in COVID-19 and need to be carefully assessed during the disease, even in patients with mild disease or asymptomatic patients. This may help in further reducing the transmission of the virus in the community.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]