Postmortem conjunctival and nasopharyngeal swabs in SARS‐CoV‐2 infected and uninfected patients

Abstract

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was declared a global pandemic by the World Health Organization (WHO) on March 11, 2020. Although the main mode of SARS-CoV-2 transmission is respiratory, studies have suggested that exposure of unprotected eyes to the virus may cause infection (Lu et al. 2020; Ulhaq & Soraya 2020). Macaque’s conjunctiva inoculated with SARS-CoV-2 led to the replication of the virus in ocular and nasopharyngeal tissue with the development of a mild interstitial pneumonia (Deng et al. 2020). Ocular manifestations, such as epiphora, conjunctival congestion or chemosis have been described to occur more frequently in patients with severe systemic manifestations (Wu et al. 2020). A recent meta-analysis found ocular manifestations among SARS-CoV-2 patients in 2–32%, with an overall pooled prevalence of 5.5% (Ulhaq & Soraya 2020). The specifity of ocular tissue/fluid in detecting SARS-CoV-2 was very low in comparison with standard sample collection from nasopharyngeal swabs (NPS) (Ulhaq & Soraya 2020). Corneal donation and transplantation are disrupted by concerns of SARS-CoV-2 tissue contamination and transmission. To date, no data are available on the postmortem prevalence of virus RNA in ocular and pharyngeal tissue in SARS-CoV-2 patients. In March 2020, the German Federal Institute for Vaccines and Biomedicines (PEI) recommended adjustments to donor screening due to SARS-CoV-2. Accordingly, in a prospective cohort study, potential corneal donors (uninfected with negative premortem NPS) in our institution had postmortem conjunctival (COS) and NPS taken starting March 17, 2020. In addition, we sampled deceased SARS-CoV-2 positive patients, with at least one positive premortem NPS (Table 1). The institutional review board of the University Hospital Aachen (EK 098/20) approved the study. All research adhered to the tenets of the Declaration of Helsinki. Informed consent was given by next of kin. Swabs were placed immediately into a sterile transport tube containing 2–3 ml of sterile saline and analysed by reverse transcriptase–polymerase chain reaction (RT-PCR; SYNLAB, Leverkusen, Germany). All values are given as mean ± standard deviation (range min–max). Because of the limited number of patients and swab results, we decided to share our findings as a descriptive statistic for continuous variables. Categorical variables were compared using the Fisher exact test. A p-value of <0.05 was considered statistically significant (IBM SPSS Statistics for Windows, Version 25, Armonk, NY, USA: IBM Corp). Included were 70 eyes of 35 SARS-CoV-2 uninfected deceased (mean age 71 ± 10 (41–81) years, 46% females, death to swab (DTS) time 29.1 ± 16.2 (8.9–70.7) hr) and 46 eyes of 23 SARS-CoV-2 positive deceased (Table 1; mean age 72 ± 10 years, 30% females, DTS time 34.5 ± 30.6 hr). The uninfected and infected group did not differ significantly in gender (p = 0.28), age (p = 0.7) or DTS time (p = 0.4). SARS-CoV-2 RNA was not detected in any postmortem NPS or COS in the uninfected group. In the SARS-CoV-2 group, four out of fourteen SARS-CoV-2 postmortem NPS were positive but no virus RNA was detected in postmortem COS (Table 1). DTS time in the positive postmortem NPS cases was 18.9 ± 11.3 (8.2–29.9) hr. Table 1 also displays the latest premortem NPS of the SARS-CoV-2 positive deceased, taken at 114.5 ± 96.3 (7.3–378.8) hours before death. They were positive at 96.1 ± 41.2 (42.1–138) hr before death in all four patients, that also had a postmortem positive NPS. However, in 36% of positive premortem NPS, no postmortem NPS was acquired. In this study, we observed that all postmortem COS were negative for SARS-CoV-2, even in cases, where the postmortem NPS was still positive. The absence of virus RNA in our postmortem swabs agrees with the literature on premortem samples, where only 3/315 COS = 0.95% (compared to NPS 604/849 = 71.1%) were positive even in symptomatic eyes, indicating that the human conjunctiva is not a typical site of SARS-CoV-2 replication (Lu et al. 2020; Seah et al. 2020; Ulhaq & Soraya 2020). Further studies are needed to investigate, whether other ocular structures, e.g. vitreous or iris, are more suitable to detect SARS-CoV-2 pre- and postmortem. In summary, our data indicate, that neither postmortem COS nor NPS can reliably exclude donors with SARS-CoV-2, particularly, when the last positive premortem NPS was obtained 90 hr or more before death.

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