RESUMEN
PURPOSE: 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.
RESUMEN
Coronavirus disease 2019 (COVID-19) is a disease caused by a new strain of coronavirus named as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Globally, since the outbreak, more than seven million confirmed cases of COVID-19 have been reported. The rapid spread and increase in the number of new cases is due to person-to-person transmission. To further control its transmission, early laboratory diagnosis of both asymptomatic and symptomatic patients is crucial. Presently, the COVID-19 diagnosis of infected individuals is dependent on computed tomography scanning and real-time polymerase chain reaction (PCR). The latter is considered more sensitive and efficient for early diagnosis. In this review, general comparisons are made (cases, fatality rate, incubation period, clinical features, and reservoirs) and diagnostic laboratory procedures (specimens, extraction methods, and positive rates by real-time PCR) are compared between SARS, Middle East Respiratory Syndrome, and SARS-2. In total, 8982 SARS-2 suspected patients specimen data were retrieved, in which 40.9% (n = 3678) were detected as positive by real-time PCR. The specimen-wise high detection rate was observed from bronchoalveolar lavage, followed by saliva, nasal swabs, and sputum. As the COVID-19 cases are persistently increasing, the selection of appropriate specimens and laboratory assay would help in rapid and timely diagnosis.