A Non-Invasive Skin Test Accurately Diagnoses Covid-19

Metabolic changes caused by Covid-19 infection can be detected in skin and saliva samples as well as in the blood, which suggest that noninvasive diagnostic tests for the disease could be available in the near future.

Investigators at the University of Surrey (United Kingdom) analyzed the correlations between serum metabolites, salivary metabolites, and skin sebum lipids in Covid-19 positive and negative individuals. In this study, 83 Covid-19 positive and negative hospitalized participants provided blood serum alongside saliva and sebum samples for analysis by liquid chromatography mass spectrometry. Participants were requested to provide all three biofluids, but due to declined consent for blood sampling, or inability to express saliva or easily provide blood, not all participants provided all three biofluids. All samples (sebum, saliva, and serum) were taken from each patient within 20 minutes of one another.

Results revealed widespread alterations to serum-sebum lipid relationships in Covid-19 positive participants versus negative controls. There was also a marked correlation between sebum lipids and the immunostimulatory hormone dehydroepiandrosterone sulfate in the Covid-19 positive group.

The biofluids were also compared in terms of their ability to differentiate COVID-19 positive participants from controls. Thus, serum performed best by multivariate analysis (sensitivity and specificity of 0.97), with the dominant changes in triglyceride and bile acid levels, in agreement with other studies identifying dyslipidemia as a hallmark of Covid-19 infection. Sebum performed well (sensitivity 0.92; specificity 0.84), with saliva performing worst (sensitivity 0.78; specificity 0.83). These findings confirmed that alterations to skin lipid profiles coincided with dyslipidaemia in serum.

Senior author Dr. Melanie Bailey, reader in analytical science the University of Surrey, said, "Covid-19 has shown us that rapid testing is vital in monitoring and identifying new illnesses. In our research, we explored the relationships between different biofluids, and what changes in one part of the human body can tell us about the overall health of a patient. Our results show that, while blood is the most accurate way of testing for this virus, skin swabs are not too far behind - in fact, the skin swab results were surprisingly accurate."

The study was published in the July 13, 2022, online edition of the journal Scientific Reports.

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