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Coronavirus can be detected in tears, study reveals

The virus that causes Covid-19 it can be detected in tears through swab tests, a flexible swab with a cotton tip used to collect material for exams. This is what reveals a research led by scientists from the University of São Paulo (USP). The results were published in the Journal of Clinical Medicine.

When analyzing samples from patients hospitalized at the Hospital das Clínicas de Bauru, in the interior of São Paulo, with a diagnosis of the disease confirmed by conventional methods, the researchers detected SARS-CoV-2 on the ocular surface using this type of test in 18.2% of the cases.

The result indicates an alternative to the nasal and oral swab, which causes discomfort in the nose and throat, and signals the need for protective measures for health professionals since, although low, there is a risk of transmission of the virus through tears.

In addition, the combination of two factors – more comorbidities and higher mortality rate – among patients with a positive tear test suggests that viral detection can help in the prognosis of the disease.

Professor Luiz Fernando Manzoni Lourençone, from the Faculty of Dentistry of Bauru and the Hospital for Rehabilitation of Craniofacial Anomalies, both at USP, says that at the beginning of the research, the research group thought of seeking an easy diagnostic method, with the collection of material without so much discomfort for the patients.

“The nasal swab, in addition to causing discomfort, is not always used correctly. For people with deviated nasal septum, for example, it can be a problem. We thought that the tear would be easier to perform, more tolerable. We managed to show that it is a path. A limitation of this study is that we do not know whether the amount of collected tears influences the positivity or not”, says Lourençone, corresponding author of the article.

According to the researcher, it is possible to infer that the probability of detecting the virus in tear samples is greater in patients with a high viral load, which can lead to viremia disseminated by various body fluids.

The work received support from the Research Support Foundation of the State of São Paulo (FAPESP) through a Scientific Initiation Scholarship granted to Luís Expedito Sabage, an undergraduate student, supervised by Lourençone.

technique

Of 61 hospitalized patients, samples were analyzed from 33 of them diagnosed with Covid-19 and another 14 without the virus, obtained during the first half of 2021, when the main variants circulating in the state of São Paulo were Gama and Delta .

Scientists used two ways to collect tears – the conjunctival swab and Schirmer strips, an exam to assess whether the eye produces enough tears. The evaluations were carried out between July and November of the same year.

Of the total, SARS-CoV-2 was detected in 18.2% of the samples collected by swab and in 12.1% of those obtained using Schirmer strips. On the other hand, as expected, none of the negative patients for Covid-19 in tests performed with nasopharyngeal swabs had a positive tear sample.

To assess comorbidities, the group adopted the Charlson Comorbidity Index (CCI), composed of 20 factors and developed as a way to standardize and adjust risk indicators, discriminating a patient’s prognosis in terms of mortality in the period of up to one year .

According to the research, individuals whose tears tested positive for SARS-CoV-2 had lower CHF compared to the rest (indicating a higher probability of death in ten years) and higher mortality rates.

Regardless of the diagnosis of Covid-19, most individuals had low tear production and ocular discomfort, indicating the need to use artificial tears during hospitalization.

In addition to demographic, clinical and ocular symptom data, the scientists worked with RT-qPCR (Reverse Transcription Polymerase Chain Reaction) analyses. The method requires the extraction of genetic material; a process of transcription of RNA into DNA and, finally, the multiplication of DNA. Considered the gold standard for diagnosing Covid-19 and widely used in several laboratories around the world, the test is capable of detecting the presence of even a single copy of the virus’s genetic material in the sample.

Unlike previous studies, in which viral genes (N and RdRp) were not considered in the RT-qPCR analyses, in this case the research identified different parts of the virus, resulting in a better detection rate.

In July 2021, the result of the work of a group from the Faculty of Medical Sciences of the State University of Campinas (Unicamp) who accompanied 83 patients admitted to the Hospital de Clínicas in the city, of which 8.43% had samples of tears or of the ocular surface positive for the disease.

“When we started, in early 2021, we did not have the technology to cross-reference some types of data, moving from basic science to clinical practice. In the meantime, Sabage did an internship at the Byers Eye Institute, in the Department of Ophthalmology at Stanford University. [Estados Unidos], a reference in studies of complex ocular fluids. With the technology there, it was possible to make several pairings and verify the presence of SARS-CoV-2 in tears from our samples. The association with another team brought results to our campus and opened a new line of research”, adds Lourençone.

Prospects

Now, the group of researchers started a new line focused on detecting diseases through tests and examinations related to the eyes. The goal is to work with other types of viruses in addition to SARS-CoV-2.

“There are other viruses that have yet to be studied in Brazil. We intend to dedicate ourselves to finding solutions and improving the quality of life for patients. We will also analyze other viral conditions that become systemic”, says the professor.

Source: CNN Brasil

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