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Cycle threshold values of SARS-CoV-2 RNA in conjunctival swabs and nasopharyngeal secretions: a comparative study from a tertiary care center in India

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Abstract

Purpose

To detect the viral RNA load of SARS-CoV-2 in conjunctival swabs of COVID-19 patients, and compare with nasopharyngeal swabs.

Methods

Conjunctival swabs of COVID-19 patients (with PCR positive nasopharyngeal swabs) were subjected to quantitative reverse transcription–polymerase chain reaction (RT-PCR) for detection of SARS-CoV-2 RNA. The cycle threshold (Ct) values of Open Reading Frame 1 (ORF 1 Ab gene) and nucleoprotein (N gene) PCRs were used to assess the viral RNA load, and compare them with the baseline values of nasopharyngeal swabs.

Results

Of 93 patients, 17 (18.27%) demonstrated SARS-CoV-2 RNA in conjunctival swabs. Baseline nasopharyngeal swabs were collected at a median of 2 days; while, the conjunctival swabs were collected at median 7 days, from onset of illness (p < 0.001). Despite a significant delay in conjunctival swab collection than nasopharyngeal swabs, the Ct values (ORF or N gene PCRs) were comparable between nasopharyngeal swab and conjunctival swab samples. Subsequently, during the recovery period, in four of these 17 patients (with conjunctival swab positivity), when the second nasopharyngeal swab was ‘negative’, the conjunctival swab was ‘positive’.

Conclusion

The conjunctival swabs demonstrated SARS-CoV-2 RNA in 17 (18.27%) of 93 COVID-19 patients. Our results may suggest a delayed or a prolonged shedding of the virus/viral RNA on the ocular surface than in nasopharyngeal mucosa.

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Acknowledgements

Abinaya Valliapan, Aditi Mehta, Anand Bhardwaj, Atul Arora, Deepti Yadav, Krinjeela Bazgain, Manik Sardana, Manjula Sharma, Monika Balyan, Khushdeep, Padma Thinlass, Pinkesh Dhariwal, Raghul Nadhan, Sabia Handa, Sraddha Limbu, Surbhi Khurana, Sushant Adiga, Uday Tekchandani, Umang Thakur, Vibha B, V Santosh (Residents of Advanced Eye Centre, PGIMER, posted in COVID-19 duty).

Funding

This work was funded by Post Graduate Institute of Medical Education and Research, Chandigarh, India (Endst No.71/261-Edu-20/2279).

Author information

Authors and Affiliations

  1. Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, 160012, India

    Reema Bansal & Vishali Gupta

  2. Department of Virology, Post Graduate Institute of Medical Education and Research, Chandigarh, India

    Ishani Bora, Poonam Kanta & Mini P. Singh

  3. Department of Medical Microbiology, Post Graduate Institute of Medical Education and Research, Chandigarh, India

    Archana Angrup & Pallab Ray

  4. Department of Internal Medicine, Post Graduate Institute of Medical Education and Research, Chandigarh, India

    Vikas Suri, Ritin Mohindra, Ashish Bhalla & Pankaj Malhotra

  5. Department of Anesthesia and Intensive Care, Post Graduate Institute of Medical Education and Research, Chandigarh, India

    Sanjay Jaswal & Shyam Charan Meena

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  1. Reema Bansal
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Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [RB], [IB], [PK] and [MPS]. The first draft of the manuscript was written by [RB] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Reema Bansal.

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Conflict of interest

None.

Ethical approval

The study was approved by the institutional ethics committee. This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Post Graduate Institute of Medical Education and Research, Chandigarh, India (Date 19.06.2020/No: PGI/IEC/2020/000688).

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Bansal, R., Bora, I., Kanta, P. et al. Cycle threshold values of SARS-CoV-2 RNA in conjunctival swabs and nasopharyngeal secretions: a comparative study from a tertiary care center in India. Int Ophthalmol 44, 29 (2024). https://doi.org/10.1007/s10792-024-02976-3

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