Investigation of SARS-CoV-2 on Ocular Surface of Coronavirus Disease 2019 Patients Using One-Step Reverse-Transcription Droplet Digital PCR

Xian Zhang,1,* Liting Chen,2,* Gaoxiang Wang,2,* Liwen Chen,1 Lifang Huang,2 Yang Cao,2 Xing Chen,2 Chaohua Deng,1 Xuhui Chen,1 Dandan Ke,1 Yuanjun Qin,1 Bo Chen,1 Xufang Sun1 1Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of China; 2Department of Hematology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of China*These authors contributed equally to this workCorrespondence: Bo Chen; Xufang SunDepartment of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1095 Jiefang Ave., Wuhan, 430030, People’s Republic of ChinaEmail eyechen@aliyun.com; sunxufang2016@163.comPurpose: This study detects SARS-CoV-2 in the ocular surface through one-step reverse-transcription droplet digital PCR (one-step RT-ddPCR) and evaluates the possibility of the ocular surface as a possible transmission route.Methods: A single-center prospective observational study was designed to investigate the viral loads in ocular surface. Specimens including the conjunctival swabs, nasopharyngeal swabs and blood were synchronously collected at a single time point for all COVID-19 patients. SARS-CoV-2 loads in nasopharyngeal swabs were tested by real-time polymerase chain reaction (PCR); the blood samples and conjunctival swabs were tested by real-time PCR and one-step RT-ddPCR.Results: Sixty-eight COVID-19 patients confirmed by nasopharyngeal real-time PCR were recruited. In the single time point test, 40 cases showed positive SARS-CoV-2 detection in either the blood, tears, or nasopharynx, of which four cases were triple-positive, 10 were dual-positive, and 26 were single-positive. The positive rate of nasopharyngeal swab real-time PCR test was 22.1% (15/68). The positive rate of blood and conjunctival swabs by one-step RT-ddPCR was 38.2% (26/68) and 25% (17/68), respectively, whereas real-time PCR was all negative. Positive conjunctival swabs were significantly correlated with positive nasopharyngeal swabs (P = 0.028). The sampling lags from illness onset to sampling day in 3 out of 4 triple-positive patients and in 9 out of 10 dual-positive patients were respectively less than 9 days and less than 20 days.Conclusion: Our results indicate that the positive rate of SARS-CoV-2 on the ocular surface is much higher than expected. Transmission possibility through the ocular surface may be greatly underestimated.Keywords: absolute quantification, virus detection, transmission, nasopharyngeal specimens, blood samples, tear samples