Coronavirus disease (COVID-19) and conjunctival sac swab findings

Background: The purpose of this article is to evaluate the positivity of conjunctival sac swab by PCR (Polymerase chain reaction) test in COronaVIrus Disease 19 (COVID-19) patients.

Methods: Inclusion criteria of our study were COVID-19 patients hospitalized during March 2021 in inpatient wards at University Hospitals in towns Bratislava and Zilina, Slovakia. The conjunctival sac swabs collected by four ophthalmologists were stored for 24 h, then analyzed in the laboratory of the Department of Microbiology and Immunology, Jessenius Faculty of Medicine in Martin, Comenius University, Slovakia. The sampling apparatus, used for conjunctival sac swab, was the Dacron polyester swab.

Results: We examined one group of 302 COVID-19 patients, 168 Male (56%) and 134 Female (44%). The patients' mean age was 66.3 ± 13.66 years, ranging from 25 to 96 years, and the mean length of hospital stay in our patients with a nasopharyngeal positive PCR test was 7.33 ± 4.76, from 2 to 24 days. The PCR tests from the conjunctival sac swabs were positive in 33 patients (11%), negative in 259 patients (86%), and ten patients (3%) were with the unclear result. In the group of 33 positive patients were 17 males with a mean age of 74.6 ± 13.59 years and 16 females with a mean age of 70.63 ± 14.17 years. The cycle threshold (C_T) values differed significantly between conjunctival sac swabs from the nasopharynx and the conjunctiva. Medians of the values were 25.1 (14.1, 32.1) and 31.5 (22.6, 36.6) (P < 0.001), respectively.

Conclusion: This study affirmed that in COVID-19 patients the SARS-CoV-2 was detectable with PCR test in conjunctival sac swab, but the positivity rate was only about one to ten cases (11%).