SARS-CoV-2 and the ocular surface: test accuracy and viral load

ABSTRACT Purpose: This study aimed to evaluate the pre-sence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in the ocular surface of individuals clinically suspected of coronavirus disease 2019 (COVID-19) and determine the accuracy of different approaches of molecular testing on the ocular surface based on the nasopharyngeal positivity status for COVID-19. Methods: A total of 152 individuals with suspected COVID-19 symptoms who simultaneously underwent nasopharyngeal and two different tear film collection techniques for quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) were included. Tears were collected and randomized: one eye had the filter strip for the Schirmer test and the contralateral eye had conjunctival swab/cytology in the inferior fornix. All patients underwent slit lamp biomicroscopy. The accuracy of various ocular surface collection techniques used for the detection of SARS-CoV-2 RNA was determined. Results: Of the 152 patients enrolled in the study, 86 (56.6%) had COVID-19 confirmed by nasopharyngeal PCR. Both tear film collection techniques detected viral particles: the Schirmer test was positive in 16.3% (14/86) and the conjunctival swab/cytology in 17.4% (15/86), with no statistically significant differences. No positive ocular tests were found among those with negative nasopharyngeal PCR tests. The overall agreement of the ocular tests was 92.7%, and in combination, the sensitivity would increase to 23.2%. The mean cycle threshold values in the nasopharyngeal, Schirmer, and conjunctival swab/cytology tests were 18.2 ± 5.3, 35.6 ± 1.4, and 36.4 ± 3.9, respectively. Compared with the nasopharyngeal test, the Schirmer (p=0.001) and conjunctival swab/cytology (p&lt;0.001) tests had significantly different Ct values. Conclusion: The Schirmer (16.3%) and conjunctival swab (17.4%) tests were comparably capable of detecting SARS-CoV-2 RNA in the ocular surface by RT-PCR accurately based on nasopharyngeal status and demonstrated indistinct sensitivity and specificity. Simultaneous specimen sampling and processing from the nasopharyngeal, Schirmer, and conjunctival swab/cytology tests demonstrated significantly lower viral load in both ocular surface approaches than in the nasopharyngeal test. Ocular manifestations detected by slit lamp biomicroscopy were not associated with ocular RT-PCR positivity.摘要 研究目的：本研究旨在评估临床疑似新型冠状病毒肺炎（coronavirus disease 2019, COVID-19）个体眼表中严重急性呼吸综合征冠状病毒2（severe acute respiratory syndrome coronavirus 2, SARS-CoV-2）核糖核酸（RNA）的存在情况，并基于新型冠状病毒肺炎鼻咽检测阳性状态，明确不同眼表分子检测方法的准确性。 研究方法：本研究共纳入152名出现疑似新型冠状病毒肺炎症状的受试者，所有受试者均同时接受鼻咽拭子检测，并采用两种不同的泪膜标本采集方法进行定量逆转录聚合酶链反应（quantitative reverse-transcriptase polymerase chain reaction, RT-qPCR）检测。泪液标本采集方式随机分配：一侧眼使用施墨试验（Schirmer test）滤纸条采集，对侧眼则于下穹窿部采集结膜拭子/细胞学标本。所有受试者均接受裂隙灯生物显微镜检查。本研究评估了各类眼表标本采集方法用于检测SARS-CoV-2 RNA的准确性。 研究结果：本研究纳入的152名受试者中，86名（56.6%）经鼻咽PCR检测确诊为新型冠状病毒肺炎。两种泪液标本采集方法均检测到病毒颗粒：施墨试验检测阳性率为16.3%（14/86），结膜拭子/细胞学检测阳性率为17.4%（15/86），二者无统计学显著差异。在鼻咽PCR检测呈阴性的受试者中，未发现眼表检测阳性病例。眼表检测的总体一致性为92.7%，联合检测时灵敏度可提升至23.2%。鼻咽拭子、施墨试验及结膜拭子/细胞学检测的平均循环阈值（cycle threshold, Ct）分别为18.2±5.3、35.6±1.4及36.4±3.9。与鼻咽拭子检测相比，施墨试验（p=0.001）与结膜拭子/细胞学检测（p<0.001）的Ct值均存在显著差异。 研究结论：基于鼻咽检测结果，施墨试验（阳性率16.3%）与结膜拭子检测（阳性率17.4%）均可通过逆转录聚合酶链反应（RT-PCR）准确检测眼表的SARS-CoV-2 RNA，二者灵敏度与特异性无显著差异。同时采集并检测鼻咽拭子、施墨试验标本及结膜拭子/细胞学标本的结果显示，两种眼表检测方法的病毒载量均显著低于鼻咽拭子检测。裂隙灯生物显微镜检查发现的眼部表现与眼表RT-PCR检测阳性结果无关联。