Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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Dr Mohan Z Mani

"Thank you very much for having published my article in record time.I would like to compliment you and your entire staff for your promptness, courtesy, and willingness to be customer friendly, which is quite unusual.I was given your reference by a colleague in pathology,and was able to directly phone your editorial office for clarifications.I would particularly like to thank the publication managers and the Assistant Editor who were following up my article. I would also like to thank you for adjusting the money I paid initially into payment for my modified article,and refunding the balance.
I wish all success to your journal and look forward to sending you any suitable similar article in future"



Dr Mohan Z Mani,
Professor & Head,
Department of Dermatolgy,
Believers Church Medical College,
Thiruvalla, Kerala
On Sep 2018




Prof. Somashekhar Nimbalkar

"Over the last few years, we have published our research regularly in Journal of Clinical and Diagnostic Research. Having published in more than 20 high impact journals over the last five years including several high impact ones and reviewing articles for even more journals across my fields of interest, we value our published work in JCDR for their high standards in publishing scientific articles. The ease of submission, the rapid reviews in under a month, the high quality of their reviewers and keen attention to the final process of proofs and publication, ensure that there are no mistakes in the final article. We have been asked clarifications on several occasions and have been happy to provide them and it exemplifies the commitment to quality of the team at JCDR."



Prof. Somashekhar Nimbalkar
Head, Department of Pediatrics, Pramukhswami Medical College, Karamsad
Chairman, Research Group, Charutar Arogya Mandal, Karamsad
National Joint Coordinator - Advanced IAP NNF NRP Program
Ex-Member, Governing Body, National Neonatology Forum, New Delhi
Ex-President - National Neonatology Forum Gujarat State Chapter
Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018




Dr. Kalyani R

"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."



Dr Kalyani R
Professor and Head
Department of Pathology
Sri Devaraj Urs Medical College
Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
On Sep 2018




Dr. Saumya Navit

"As a peer-reviewed journal, the Journal of Clinical and Diagnostic Research provides an opportunity to researchers, scientists and budding professionals to explore the developments in the field of medicine and dentistry and their varied specialities, thus extending our view on biological diversities of living species in relation to medicine.
‘Knowledge is treasure of a wise man.’ The free access of this journal provides an immense scope of learning for the both the old and the young in field of medicine and dentistry as well. The multidisciplinary nature of the journal makes it a better platform to absorb all that is being researched and developed. The publication process is systematic and professional. Online submission, publication and peer reviewing makes it a user-friendly journal.
As an experienced dentist and an academician, I proudly recommend this journal to the dental fraternity as a good quality open access platform for rapid communication of their cutting-edge research progress and discovery.
I wish JCDR a great success and I hope that journal will soar higher with the passing time."



Dr Saumya Navit
Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
Lucknow
On Sep 2018




Dr. Arunava Biswas

"My sincere attachment with JCDR as an author as well as reviewer is a learning experience . Their systematic approach in publication of article in various categories is really praiseworthy.
Their prompt and timely response to review's query and the manner in which they have set the reviewing process helps in extracting the best possible scientific writings for publication.
It's a honour and pride to be a part of the JCDR team. My very best wishes to JCDR and hope it will sparkle up above the sky as a high indexed journal in near future."



Dr. Arunava Biswas
MD, DM (Clinical Pharmacology)
Assistant Professor
Department of Pharmacology
Calcutta National Medical College & Hospital , Kolkata




Dr. C.S. Ramesh Babu
" Journal of Clinical and Diagnostic Research (JCDR) is a multi-specialty medical and dental journal publishing high quality research articles in almost all branches of medicine. The quality of printing of figures and tables is excellent and comparable to any International journal. An added advantage is nominal publication charges and monthly issue of the journal and more chances of an article being accepted for publication. Moreover being a multi-specialty journal an article concerning a particular specialty has a wider reach of readers of other related specialties also. As an author and reviewer for several years I find this Journal most suitable and highly recommend this Journal."
Best regards,
C.S. Ramesh Babu,
Associate Professor of Anatomy,
Muzaffarnagar Medical College,
Muzaffarnagar.
On Aug 2018




Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".



Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
Bengaluru.
On Aug 2018




Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help one’s reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".



Dr. Mamta Gupta
Consultant
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018




Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.


Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."



Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011




Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."



Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011
Anuradha

Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.


Dr. Anuradha
E-mail: anuradha2nittur@gmail.com
On Jan 2020

Important Notice

Original article / research
Year : 2022 | Month : January | Volume : 16 | Issue : 1 | Page : DC01 - DC05 Full Version

Diagnostic Accuracy of STANDARD Q COVID-19 Antigen Detection Kit in Comparison with RT-PCR Assay using Nasopharyngeal Samples in India


Published: January 1, 2022 | DOI: https://doi.org/10.7860/JCDR/2022/52286.15825
Seema Aleem, Naziya Zahoor, Asif Jeelani, SM Salim Khan

1. Senior Resident, Department of Microbiology, Government Medical College, Srinagar, Jammu and Kashmir, India. 2. Senior Resident, Department of Community Medicine, Government Medical College, Srinagar, Jammu and Kashmir, India. 3. Senior Resident, Department of Community Medicine, Government Medical College, Srinagar, Jammu and Kashmir, India. 4. Professor and Head, Department of Community Medicine, Government Medical College, Srinagar, Jammu and Kashmir, India.

Correspondence Address :
Dr. Asif Jeelani,
House No. 27, Lane No. 1, Lal Bazar, Srinagar, Jammu and Kashmir, India.
E-mail: drasifjeelani@gmail.com

Abstract

Introduction: Real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) can be considered to be the gold standard for diagnosis of Coronavirus Disease-2019 (COVID-19). Though it is highly accurate but has some limitations in terms of its use, which means that Rapid Antigen Tests (RAT) can support COVID-19 mitigation efforts.

Aim: To estimate sensitivity, specificity and degree of agreement of STANDARD Q COVID-19 Antigen Detection Kit in comparison to real-time quantitative RT-PCR (qRT-PCR).

Materials and Methods: This cross-sectional study was conducted at Government Medical College, Srinagar, Jammu and Kashmir, India, in April 2021. Socio-demographic and clinical information was collected on a pretested schedule after which two consecutive nasopharyngeal swabs were collected from each subject. One sample was tested using the STANDARD Q COVID-19 antigen test and the other was tested using qRT-PCR. Sensitivity and specificity were calculated using standard formulas. Cohen’s Kappa was calculated and Mann-Whitney U test was used for comparison.

Results: The study included 473 subjects with a mean age of 38.4±12.2 years. Around 1/4th (124 subjects) of subjects were symptomatic at testing with the most common symptoms being fever (57.2%), cough (50%), sore throat (43%), myalgia (25%) and diarrhoea (13%). The sensitivity, specificity, positive likelihood ratio and negative likelihood ratio were estimated to be 54.4%, 99.2%, 71.49 and 0.46, respectively. The Cohen’s Kappa between the two tests was 0.644. Cycle threshold value was significantly lower in subjects with symptoms and those with a positive rapid test among those positive on qRT-PCR.

Conclusion: The STANDARD Q COVID-19 antigen test has a reasonable sensitivity, high specificity with a substantial inter-test agreement in comparison to qRT-PCR.

Keywords

Coronavirus disease-2019, Rapid antigen, Reverse transcription polymerase chain reaction, Sensitivity, Specificity

The Coronavirus Disease-2019 (COVID-19) pandemic led to significant morbidity, mortality in addition to unprecedented disruption of economic activities globally (1),(2). A total of 183 million cases and more than 3.9 million deaths have been reported globally till June 2021. India accounted for around 30 million cases and 0.4 million deaths of these numbers till June 2021 (3). It has undone decades of improvement made in health of the communities and it is imperative to bring this pandemic under control so that a concerted global effort is made towards achieving Sustainable Development Goals (4),(5). Mitigating the COVID-19 pandemic will require multipronged interventions but augmentation of testing capacity is one of the core strategies that were advocated by the World Health Organisation (WHO) (6). Testing formed one of the main components of what came to be known as Test-Trace-Isolate-Treat strategy (7).

Timely and accurate diagnosis of COVID-19 is essential for limiting the spread and early clinical management of COVID-19 (8). Real-Time quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) is considered as the gold standard test for detection of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) owing to its high sensitivity and specificity but the requirement of special equipment, long turnover time, high cost and need for skilled staff limit its use in the field settings (9),(10). A need for a rapid and less resource-intensive antigen detection assay was felt early in the course of this pandemic and multiple RAT were developed (6). Despite having lower sensitivity and specificity than the conventional qRT-PCR, these tests still are an important tool for mitigation of COVID-19 pandemic particularly in field/community settings (11),(12).

These rapid diagnostic tests are easy to perform, did not require specialised laboratory support and can easily be done at point of care. These benefits need to be balanced with the decrease in diagnostic accuracy and that needs data regarding the diagnostic accuracy of these Rapid Antigen Tests (RAT). The present study was conducted with the purpose of estimating the diagnostic accuracy of one rapid antigen diagnostic kit in comparison to qRT-PCR tests.

The objectives of the study were:

• To estimate the sensitivity and specificity of STANDARD Q RAT in comparison to qRT-PCR for COVID-19.
• To estimate the degree of agreement between the two diagnostic tests.

Material and Methods

A cross-sectional study was conducted by Government Medical College, Srinagar, Jammu and Kashmir, India, at one urban health center affiliated with the Department of Community Medicine. Samples for the two tests were collected between 1st to 30th April 2021. The health facility was one of the designated COVID-19 testing centres. Testing services were provided on all days and subjects included those referred from Outpatient Department (OPD), contacts of positive patients and those requiring testing for any other criteria like before undertaking travel or any elective procedure. The centre conducted an average of 150 tests daily during April 2021. The study was approved by Institutional Review Board of the Institution (No. GMCS/EC/2021/109) and informed consent was taken from all subjects and only subjects who provided informed consent were included in the study. The study period corresponded to time just after the peak of the deadly second wave in India. (Table/Fig 1) has depicting the time period when the study was conducted.

Sample size calculation: Sample size was calculated using Buderer’s formula at 95% confidence level with an expected sensitivity of 70%, expected specificity of 95%, a precision of 10%. The sample size was estimated to be 359. A total of 473 were included in the study (12),(13).

Inclusion criteria: All subjects aged 18 years and above who reported to the health facility for testing were included in the study.

Exclusion criteria: Subjects coming for repeat testing, subjects with a history of recent facial trauma/fracture/surgery, subjects with bleeding disorders, mucositis (14),(15).

A total of 512 subjects met the inclusion criteria of which 475 subjects provided consent. Of these 2 subjects were excluded as there qRT-PCR was inconclusive.

Interview schedule and sample collection: Data was collected on a pretested and structured schedule that collected information regarding the subject’s age, gender, clinical features and the primary reason for testing. The data elements to be included were developed from the sample referral form developed by Indian Council of Medical Research (ICMR) for collection of qRT-PCR samples (16),(17),(18). The schedule was pretested on 20 subjects. Data from these 20 subjects was excluded from the present study.

Case Definitions Used

Standard case definitions as provided by National Center for Disease Control were used for defining a contact who were then categorised as high risk and low risk based on same case definitions (19),(20).

COVID-19 contact: A contact was defined as any individual who met any one of the three criteria: (1) Stayed in same close environment of a laboratory confirmed COVID-19 patient; (2) Travelled together in close proximity (1m) with a symptomatic person who later tested positive for COVID-19; (3) Provided direct care without proper Personal Protective Equipment (PPE) for COVID-19 patients (20).

High risk contact: A contact who touched body fluids of the patient without PPE, had direct physical contact with the body of patient including physical examination without PPE, touched or cleaned the linens, clothes or dishes of patient, lives in same household as the patient, within 1 metre of confirmed case without precautions (20).

Low risk contact: A contact who did not meet the above criteria was labelled as low risk contact (20).

Procedure

Testing procedure: The subject was made to sit comfortably and a repeat consent taken. A nasopharyngeal swab for qRT-PCR was collected first under proper aseptic procedures and as per the recommended procedure by a trained laboratory technician (15),(21). The swab was sealed in viral transport medium, labelled and stored in a cold chain (2-8oC) for transportation to the laboratory. A second nasopharyngeal sample was collected by the same technician and the sample was processed for RAT. The test was done as per the manufacturer’s guidelines mentioned in the product inlet. Briefly, the nasopharyngeal swab was put in the buffer medium provided with the kit. The swab was kept in the buffer for 15 seconds. After this the swab was withdrawn while squeezing the sides of buffer tube. The rapid card was then kept on level surface and three drops from the buffer mixture were put in sample well. The results were read after 15 minutes and the same was communicated to the subject. The RAT was done using STANDARD Q COVID-19 (SD Biosensor, Inc. Republic of Korea). STANDARD Q COVID-19 Antigen Test is a rapid chromatographic immunoassay for the qualitative detection of SARS-CoV-2 (19). The result was read as positive, negative, invalid (if no control line was shown). Repeat sampling was done for subjects with invalid tests and then categorised as positive and negative (22). Subjects with a positive RAT were advised to contact the concerned health facilities.

Processing swabs collected for qRT-PCR: All the qRT-PCR samples collected in a single day were sent to the qRT-PCR laboratory at the end of each day. The samples were transported under proper precautions and were processed on same day of collection. A volume of 200 µL was collected from each Viral Transport Medium (VTM) and processed further for Ribonucleic Acid (RNA) extraction (23). Single step RT-PCR for SARS-CoV-2 targeting the E gene was conducted on the sample. A Cycle threshold (Ct) value of less than 35 was reported as positive (24).

Bias: Sample for qRT-PCR was taken before RAT to avoid any bias owing to prior knowledge of COVID-19 status of subjects by technicians. The qRT-PCR Laboratory was not aware of the result on RATs.

Variables: The primary variables collected were basic clinical information and test results for RAT/RT-PCR. Sensitivity, specificity, Positive Predictive Values (PPV) and Negative Predictive Values (NPV) and Cohen’s Kappa were calculated (25)

Main outcome measures:

• Sensitivity and specificity for the RAT kit.
• Cohen’s Kappa score for agreement between the two tests.
• Cycle threshold value of positive samples.

Statistical Analysis

Socio-demographic and clinical profile was described using percentages and mean. Sensitivity, Specificity, PPV and NPV of RAT was calculated using relevant formulas by keeping qRT-PCR as a gold standard. Cohen’s Kappa was calculated. Ct values between two groups were compared by Mann-Whitney U test. The p-value of less than 0.05 was considered to be statistically significant (26).

Results

A total of 475 subjects provided simultaneous samples for both tests of which two samples were reported as rejected in qRT-PCR. Both these subjects had a negative rapid test and were excluded from the final analysis. A total of 473 subjects were included in the final analysis. The selection of study subjects in depicted in (Table/Fig 2). The subjects comprised of 277 (58.6%) males and 196 (41.4) females. The mean age of subjects was 38.4±12.2 years and 57.29% of subjects belonged to urban areas. A total of 124 subjects (26.2%) had symptom at the time of testing. The most common presenting symptom was fever reported by 71 subjects (15.01%). Loss of smell was reported by seven (1.48%) subjects. Total 13.1% subjects had a previous history of COVID-19. The primary reason for testing included a positive contact history 221(46.7%) subjects, symptoms 124(26.2%) and voluntary testing 116 (24.5%). A total of 1/5th of subjects had any concomitant co-morbidity. The socio-clinical profile of subjects is described in (Table/Fig 3).

Of the 473 subjects, 79 (16.7%) were positive on qRT-PCR of which 43 (54.4%) subjects were positive on RAT as well. Overall positivity rate was 16.7% and 9.7% on qRT-PCR and RAT respectively. These results have been depicted in (Table/Fig 4).

Considering qRT-PCR as the gold standard, the sensitivity and specificity were estimated at 54.43% (42.83%-65.69%) and 99.24% (97.79% to 99.84%), respectively. Positive Likelihood Ratio (PLR), Negative Likelihood Ratio (NLR), PPV and NPV are depicted in (Table/Fig 5). The Cohen’s Kappa between the two was 0.644 (95% CI:0.543-0.745) which depicted a fair level of agreement between the two tests. Authors compared Ct values of subjects positive on qRT-PCR on the basis of their symptoms and their results on Rapid tests. Symptomatic subjects had a significantly lower Ct values than asymptomatic subjects. Similarly subjects positive of RAT had a lower Ct value than those negative on RAT. The median cycle threshold value of rapid antigen-positive subjects was 19 (range 16-30) and was 33 (range 24-35) for RAT negative cases. The median Ct value among symptomatic subjects was significantly lower (20) than asymptomatic subjects (32). The detailed values are depicted in (Table/Fig 6). The mean cycle threshold value of positive subjects was 25.6±6.7 with a range of 16-35. The Ct values were associated with the presence or absence of symptoms but not with the duration of illness (Table/Fig 7).

Discussion

The qRT-PCR is the gold standard test for detection of SARS-CoV-2 in respiratory specimens but its long turnover time and need for sophisticated equipment limit its use. RAT can complement qRT-PCR in the diagnosis of COVID-19 in specific settings. This study evaluated the performance of RAT in comparison with qRT-PCR.

The present study estimated the sensitivity and specificity of RAT to be 54.43% (42.83% to 65.69%) and 99.24 (97.79% to 99.84%), respectively. The overall accuracy was estimated at 91.75%. The sensitivity may appear to be very low but its high specificity coupled with almost instantaneous test report mean that it can augment testing capacity in specific settings. The sensitivity is comparable to a previous study done in Belgium by Lambert-Niclot S et al., and another study by Ristic M et al., in Serbia (27),(28). The sensitivity is also comparable to that estimated for nasopharyngeal swabs by Yamayoshi S et al., (29). Igloi Z et al., conducted a similar study in Netherlands using the same rapid antigen kits and reported a much higher sensitivity of 84% (30). The overall qRT-PCR positivity rate of 16.7% in our study is comparable to the positivity rate of 19% in that study. The higher sensitivity of 84% in their study may have been on account of higher proportion of symptomatic subjects than in their study. Of those positive on qRT-PCR in our study, 56.9% were symptomatic at the time of testing whereas 74% of subjects in the study by Igloi Z et al., were symptomatic (30). Another study conducted by Cerutti F et al., also reported higher sensitivity of 70.6%, the study had included only symptomatic subjects at the time of testing (8). Another previous similar studies conducted in Spain and another one in Uganda have reported higher sensitivity in the range of 70% but those studies had a higher proportion of symptomatic subjects in the sample (31),(32). The sensitivity is higher than one previous study conducted in Brussels and one more study by Lee J et al., (33).

Authors estimated that the STANDARD Q rapid test had a very high specificity. This is comparable to multiple previous studies that also found the specificity to be more than 98% (8),(33),(34). It infers that rapid antigen kits have very less likelihood to give false positive results and a subject with a positive test should be considered positive for SARS-CoV-2. All test kits have to apply for validation before actual use and the regulatory authorities in India have kept minimum acceptance criteria of 50% sensitivity and 95% specificity for point of care tests which are used in a field setting without laboratory support (21). The test kit used in our study met both these criteria.

Cycle threshold (Ct) value for qRT-PCR has been a subject of great debate in recent times. As Ct value refers to the number of replication cycles required for detection of viral RNA, many studies have tried to estimate the clinical implications of Ct values particularly its implications in determining viral loads and clinical severity (35),(36). Of the subjects positive on qRT-PCR in our study, Ct values ranged from 16 to 35. The values were significantly lower for symptomatic subjects in comparison to asymptomatic subjects for SARS-CoV-2 positive subjects. Symptomatic subjects had a median Ct Value of 20 (IQR 18-25) which was significantly lower than the Ct Value of asymptomatic subjects 32 (IQR 30-34). This supports the results from multiple other studies and can be explained that symptomatic patients have a higher viral load (35),(36). This has implications in deciding the level of protection. Studies by Cerutti F et al., and Igloi Z et al., have also found lower Ct values/ higher viral load among symptomatic subjects in comparison to asymptomatic subjects (8),(30). It may also translate to higher infectiousness among symptomatic subjects and therefore enhanced personal protection may be required when dealing with symptomatic patients as compared to asymptomatic patients. Most of the symptomatic subjects were on day 2nd or 3rd of their illness with only five symptomatic subjects having an illness duration of six or more days. The duration of illness had no significant relation with Ct values which could be due to a smaller number of subjects with a duration of illness of more than six days.

The present study also found a significantly lower Ct values for subjects positive on RATs as well. The median Ct value of subjects positive on rapid tests was 19 in comparison to 33 for those negative of RAT. Studies by Cerutti F et al., and a study by Igloi Z et al., also found that the sensitivity of rapid tests increases with lower Ct values (8),(30). In other words, subjects who are positive on RAT are more likely to have lower Ct values. These supports the growing body of evidence that lower Ct values means higher viral loads which inturn increase the probability of a positive RAT (27),(28). The strengths of the study included that only a single trained laboratory technician collected the samples and qRT-PCR samples were processed on the same day. Rapid tests and qRT-PCR results were read by different persons to avoid any bias.

Limitation(s)

The major limitation of this study is the lack of a true gold standard as multiple studies have estimated the sensitivity and specificity of qRT-PCR to be between 70-80%. This results in uncertainty in labelling samples as true positives and negatives. One more limitation was the low number of subjects with an illness duration of more than six days which decreased the power of this study to estimate the trend of Cycle threshold value with days of illness.

Conclusion

The STANDARD Q RAT has reasonable sensitivity and high specificity. The two tests have a substantial inter-test agreement. Sensitivity was specifically high in those symptomatic at the time of testing. This can particularly be helpful in early identification followed by isolation/treatment of symptomatic subjects which otherwise can get delayed if only qRT-PCR is available. Using both of these tests together and following up a RAT negative person with qRT-PCR will enhance the overall sensitivity.

Acknowledgement

The authors would like to thank Ms. Gousia (laboratory technician) and other support staff who were involved in sample collection, processing and interpretation of results.

b#bAuthor’s contribution:b?b All the authors contributed to the conceptualization of study design, interpretation of data and the drafting of the article. NK, SA and AJ were also involved in data collection, acquisition and in finalizing the manuscript.

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DOI and Others

DOI: 10.7860/JCDR/2022/52286.15825

Date of Submission: Sep 06, 2021
Date of Peer Review: Nov 03, 2021
Date of Acceptance: Dec 01, 2021
Date of Publishing: Jan 01, 2022

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. No

PLAGIARISM CHECKING METHODS:
• Plagiarism X-checker: Sep 07, 2021
• Manual Googling: Oct 29, 2021
• iThenticate Software: Nov 26, 2021 (10%)

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