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Using human tears for rapid, non-invasive diagnosis of COVID-19

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Dr Anjali Prashar, author of the book, “Shed Tears for Diagnostics, writes that since tear fluid represents a novel source of biomarkers for not just ocular diseases but also systemic diseases like flu, research needs to be conducted on whether human tears could be used for rapid, non-invasive diagnosis of SARS-CoV-2 infections as well

Surrounded by a blanket of tears the world mourns the death of humankind!

When we think of any living species, we associate very easily with ‘DNA’. To think that this deadly coronavirus is not even ‘DNA’ and yet is able to cause mayhem all over the world is incogitable.

SARS or severe acute respiratory syndrome is a viral respiratory disease produced by a coronavirus called SARS-associated coronavirus (SARS-CoV) and SARS-CoV-2 is the causative coronavirus of COVID-19. Several techniques have been suggested and are being used for the detection of this deadly condition. But science continues to strive towards exploring newer, faster techniques in a race to curtail human suffering and subsequently the shedding of tears. So what if we turn the tables around a little and say ‘It will all begin with tears but end with a smile’.

Presenting here a novel concept for COVID diagnostics which will literally make you cry.

So what we understand of the clear watery liquid trickling down from our eyes as simple human tears is actually a complex biochemical concoction comprising proteins, carbohydrates and god knows what or rather the scientist knows what. Incidentally the tear fluid represents a novel source of biomarkers for not only ocular diseases but also systemic diseases like flu.

Tears essentially provide for a non-invasive, cost-effective, rapid detection platform. Interestingly ‘dried up tears’ end up in unique fern like patterns; the process is termed as tear ferning. Typically tears (1 or 2 microlitres) are placed on a microscopy glass slide and allowed to dry by evaporation at room temp. Within 10 min mucus crystallisation can be observed under a simple light microscope.

Typically, a crystallised pattern in the form of a tear fern is obtained and is reliant on the electrolyte, protein and mucus content of the tears. The fern reveals the functionality of the tears. The ferning phenomenon is thought to occur due to varied ratios of sodium, potassium, magnesium and calcium ions.

For a layman to understand this, an organised patterned fern represents healthy tears and hence healthy individuals. Fern break up or distorted fern is representative of disease. Basis that some tear electrolyte (s) concentrations would vary in the COVID state this method may be used as a ‘first line of detection’.

All it needs is some quick experimental data that can be easily obtained from labs and hospitals pan-India from patients with minimal equipment namely a filter paper, a microscope and a glass slide. We need to look for specific identifiable fragmented patterns. If this works as a low-cost infection-indicator the method will allow for mass screening of normal, suspect, infected as well as convalescent populations.

Going further, a deeper scientific scenario would involve exploring tear samples for a change in the levels of one (or more) protein (s) or any other tear constituent in the corona patient. This target is what would stand as the ultimate biomarker of COVID-19. Since tears can be obtained only in small (microliter) quantities, microfluidics may be used in developing a kit for rapid detection.

Remarkably, this tear diagnostic platform is not limited to ocular conditions, although it would additionally help in exploring ocular manifestations in COVID-19 patients. Further studies on these lines would be invaluable in asymptomatic patients as well as for early disease detection. Monitoring of patient response to therapeutics will also be plausible. In general, predictive, preventive and personalised medicine will all hugely benefit from tear diagnostics in the future.

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