Research led by scientists on the University of São Paulo (USP) in Brazil has found that the coronavirus that causes COVID-19 might be detected in tears collected by swabbing. A swab is an absorbent cotton pad on a versatile rod used to scrub wounds, apply medication and take specimens.
The researchers analyzed samples from patients diagnosed with the disease by conventional methods and admitted to the Hospital for Rehabilitation of Craniofacial Anomalies (HRAC) run by the Bauru Dental School (FOB-USP). SARS-CoV-2 was detected in 18.2% of the samples, suggesting this method could possibly be an alternative choice to nasopharyngeal swabbing, which is unpleasant, and that health staff should take steps to guard themselves against infection via patients’ tears, although the danger is admittedly low.
Furthermore, a mix of two aspects – more comorbidities and a better mortality rate – amongst patients whose tear samples tested positive suggests that this approach to detection of the virus could possibly be a prognosis predictor.
The study is reported in an article published within the November 2022 issue of the Journal of Clinical Medicine.
Initially, we got down to develop a diagnostic test based on easier collection of fabric without causing patient discomfort. Nasal and nasopharyngeal swabbing just isn’t only unpleasant but additionally often performed incorrectly. For individuals with a nasal septum deviation, it could actually be an issue. We took the view that tear sampling could be easy to execute and more tolerable. We succeeded in showing this to be feasible. Amongst the restrictions of the study was not knowing whether the quantity of liquid collected for the test influences its result.”
Luiz Fernando Manzoni Lourençone, professor of drugs at HRAC and last writer of the article
The findings suggest that the probability of detecting the virus in tears is bigger when the patient has a high viral load, which may result in viremia in body fluids, he added.
The study was supported by FAPESP via a scientific initiation scholarship awarded to Luís Expedito Sabage, an undergraduate student supervised by Lourençone.
Technique
The study cohort comprised 61 hospitalized patients, with 28 testing negative and 33 positive for COVID-19 by RT-qPCR via nasopharyngeal swab. Tears were analyzed from all 33 positives and from 14 of the 28 negatives. The tears were collected in the primary half of 2021 when the fundamental viral variants circulating in São Paulo state were gamma and delta.
Along with collection by conjunctival swab, the scientists also used a method often known as the Schirmer strip test, during which a strip of filter paper is placed for five minutes contained in the lower eyelid (normally used to find out whether the attention produces enough tears). The samples were analyzed between July and November 2021.
SARS-CoV-2 was detected in 18.2% of the samples collected by conjunctival swab and 12.1% of those collected by Schirmer strip. As expected, not one of the patients who tested negative for the virus via nasopharyngeal swab had tears that tested positive.
The Charlson Comorbidity Index (CCI) was used to predict risk of death inside a 12 months of hospitalization for patients with 20 specific conditions. Patients with SARS-CoV-2 particles in tear samples had an almost sevenfold probability of dying in comparison with patients with a negative result. Those patients also had other aspects that might contribute to death, similar to a poor ten-year survival rate based on CCI.
A lot of the patients had low tear production and eye discomfort no matter their COVID-19 diagnosis, possibly pointing to the necessity for artificial tear use during hospitalization, in line with the authors.
The study also included demographic, clinical and ocular symptom data. The fundamental diagnostic test used was real-time quantitative PCR (polymerase chain response), which may detect a single copy of viral RNA in a sample and is taken into account the gold standard for diagnosing COVID-19 by clinical evaluation laboratories all over the world.
Innovating as compared with previous research, on this study viral RNA positivity was determined way more precisely by analyzing the nucleocapsid (N), envelope (E) and RNA-dependent RNA polymerase (RdRp).
An article published in July 2021 in Experimental Biology and Medicine by a bunch of researchers on the State University of Campinas’s School of Medical Sciences (FCM-UNICAMP), also in São Paulo state, reported the outcomes of a study conducted at its teaching hospital where SARS-CoV-2 was detected in tear samples from 8.43% of the 83 patients enrolled within the study.
“Once we began, in early 2021, we lacked the technology to cross-reference certain sorts of data as a route out of basic science and into clinical practice. Since then, Sabage has worked as a research intern at Stanford University’s Byers Eye Institute [in the United States], a number one center for advanced studies of ocular fluids. Their technology enabled us to detect several correlations and make sure the presence of SARS-CoV-2 in our tear samples. Partnering with one other team brought results for our campus and opened up a recent research line,” Lourençone said.
The internship at Stanford was supported by FAPESP.
Possibilities
The research group has now begun working on a recent line that focuses on detecting other viral diseases via tests and analyses referring to the eyes. “Many viruses have not been studied sufficiently in Brazil. We wish to develop solutions that improve the standard of life for patients. We plan to research other viral conditions that grow to be systemic,” he said.
Source:
São Paulo Research Foundation (FAPESP)
Journal reference:
Sabage, L.E., et al. (2022) Conjunctival Swabs Reveal Higher Detection Rate In comparison with Schirmer Strips for SARS-CoV-2 RNA Detection in Tears of Hospitalized COVID-19 Patients. Journal of Clinical Medicine. doi.org/10.3390/jcm11236929.