Evaluation of SARS-CoV-2 in Tears of Patients with Moderate to Severe COVID-19

Abstract

Purpose: To investigate the presence of SARS-CoV-2 RNA in tears of patients with moderate to severe coronavirus disease 2019 (COVID-19).

Design: Cross-sectional study.

Participants: Patients with laboratory-proven moderate to severe COVID-19.

Methods: Tears were collected within 48 hours of laboratory confirmation using 3 methods: conjunctival swab plus Schirmer's test strips (group 1), conjunctival swab (group 2), and Schirmer's test strips (group 3). Samples from both the eyes of each patient were transported in a single viral transport media for real-time RT-PCR. Detailed demographic profiles, systemic symptoms, comorbidities, and ocular manifestations were noted.

Main outcome measures: Viral load of a sample was determined using cycle threshold (Ct) value of E gene. A specimen was considered to show positive results if the amplification curve for the E gene crossed the threshold line within 35 cycles and if it showed positive results on an RNA-dependent RNA polymerase or open reading frame 1b gene assay.

Results: Of the 78 patients enrolled in the study, samples from 3 patients were found to be inadequate for analysis. Thirty-six patients (48%) had moderate disease, whereas 39 patients (52%) had severe disease, with no ocular involvement in any patient. In the 75 patients, RT-PCR analysis of tears showed positive results in 18 patients (24%), and 29 of 225 samples (12.9%) showed positive results. Positive results were found in 11 (14.7%), 11 (14.7%), and 7 (9.3%) patients in groups 1, 2, and 3, respectively (P = 0.3105). Mean Ct values in groups 1, 2, and 3 were 28.36 ± 6.15, 29.00 ± 5.58, and 27.86 ± 6.46 (P = 0.92), respectively. Five patients showed positive RT-PCR results by all 3 methods (mean Ct value, 25.24 ± 6.33), and 12 patients showed positive results by any of the 3 methods (mean Ct value, 32.16 ± 1.94), the difference in Ct values being statistically significant (P = 0.029). The median value of symptomatology in patients with positive RT-PCR results from tears was 5 days (range, 4-9 days).

Conclusions: SARS-CoV-2 RNA was detected in tears of 24% of patients with laboratory-proven moderate to severe COVID-19. Conjunctival swab remains the gold standard of tear collection for RT-PCR assay. A significantly higher possibility of viral transmission exists through tears in patients with moderate to severe COVID-19.

Keywords: COVID-19; Conjunctival swab; Nasopharyngeal swab; Reverse-transcriptase polymerase chain reaction; SARS-CoV-2.

Figure 1

Flowchart depicting the study design. COVID-19 = coronavirus disease 2019; RT-PCR = reverse-transcriptase polymerase chain reaction; VTM = viral transport media.

Figure 2

Boxplot showing the cyclic threshold (Ct) value of E gene, Ct value of ORF1b gene, and duration of coronavirus disease 2019 symptoms in the 3 groups in patients with positive reverse-transcriptase polymerase chain reaction results in tears.