Novel Point-Of-Care Test To Distinguish Bacterial From Viral Infection Moves Closer To Clinic

In a proof-of-principle study, researchers demonstrated that a two-gene RNA signature can distinguish bacterial from viral infections in blood samples from children, paving the way to a point-of-care (POC) test that could do the same in the clinic.

Currently available tests to distinguish children with bacterial infection from those with viral infections "are unreliable, and as a result many children are treated unnecessarily with antibiotics, while others with severe bacterial infections are 'missed,' resulting in delayed diagnosis, often with fatal consequences," Dr. Michael Levin of Imperial College London told Reuters Health by email.

The new approach detects immune responses to pathogens, which differ between bacterial and viral infections, he explained. The test detects gene activation through changes in pH, with the readout being electrical signals that can be read on a mobile phone or computer, "making detection both rapid, and potentially very cheap," he said.

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For their JAMA Pediatrics study, Dr. Levin and colleagues randomly selected RNA samples from 12 children with bacterial infection and 12 with viral infection, matched for severity. The samples came from the Inflammatory and Infectious Disease Study (IRIS), which earlier had identified a two-transcript gene signature (IFI44L and FAM89A) that could discriminate between the two types of infection.

With their laboratory-on-chip platform, which uses reverse transcription loop-mediated isothermal amplification (RT-LAMP), the team compared gene expression values and assigned a score to each patient reflecting risk of bacterial or viral disease.

When applied to microarray data, the two-transcript signature had 100% sensitivity and specificity, with an area under the curve of 100%, as well. Translating the signature to RT-eLAMP showed the same results: 100% sensitivity and specificity, with an AUC of 100%.

The authors state, "While our study includes modest patient numbers, it provides a proof of concept that host RNA signatures can be detected rapidly and cost-effectively in a format suitable for development as a point-of-care diagnostic test that might be applied to a range of clinical diagnoses."

Dr. Levin said, "We now need to scale up, and repeat the study on much larger numbers of children (and adults) with fever and suspected infection. To undertake a large-scale clinical evaluation, we need production of large numbers of the prototype test, and evaluation of the test device in hospitals and clinics in different countries."

Dr. Kagya Amoako, Director, Biomaterials and Medical Device Innovation Laboratory and Founding Director and Coordinator of the Graduate Biomedical Engineering Program at the University of New Haven in Connecticut, commented by email to Reuters Health. "With an acceptable safety and efficacy profile, the device would have an early detection advantage over antibody detection test kits," he said. "A viral infection could be detected earlier, and remedies deployed sooner rather than waiting for antibodies to viral infections to develop further down the disease progression before the infection is diagnosed."

"In addition," he noted, "a POC device able to detect RNA at the accuracy level of PCR, even if by indirect means. can be impactful in epidemiology."

Nonetheless, he added, "false-positive and false-negative error rates seen with rapid test kits for SARS-CoV-2 antibodies have been problematic, and thus how this new potential POC device will overcome error rates in the detection of host RNA and differentiating bacterial and viral origins is critical."

"Bacterial and viral strain specificities are equally important metrics for such a device, as a binary output of either a viral or bacterial RNA detection leaves critical insights unaddressed," he said.

Like Dr. Levin, he noted that the device "needs to be further vetted from a larger sample size of randomized patient studies."

Dr. Levin and colleagues have patents pending related to the study.

—Marilynn Larkin

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