Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. Acute respiratory infections are one of the most common reasons for people to present to primary care and decisions about whether or not to prescribe antibiotics might rely on point-of-care tests for inflammation. The relevant Cochrane review was updated in October 2022 and we asked new lead author, Siri Aas Smedemark from Odense University Hospital in Denmark, to tell us more in this podcast.

Siri: The first version of this review of using biomarkers as point‐of‐care tests to guide the prescribing of antibiotics in people with acute respiratory infections, or ARIs, in primary care concluded, in 2014, that adding C-reactive protein tests to the clinical examination is likely to reduce antibiotic use in these patients, without affecting recovery rates or the duration of illness.
These tests are now widely used in primary care in many European countries, but antibiotic resistance is still of concern and remains a public health priority according to the World Health Organisation. Antibiotic resistance leads to ineffective treatments, increased risk of serious complications, such as bacterial infections and death, and increased healthcare costs. Therefore, given that ARIs are still often treated with antibiotics in primary care settings, even though many of these infections are self‐limiting and frequently of viral origin, we have re-visited the evidence to bring in studies conducted since 2014.
A point‐of‐care biomarker test of inflammation identifies part of the acute phase response to tissue injury, regardless of whether it is due to infection, trauma or inflammation. A normal or low level of the biomarker could rule out a serious bacterial infection and may help the doctor to decide whether to use an antibiotic. In other words, these biomarkers may help identify patients who would not benefit from antibiotic treatment.
Therefore, for this update, in June 2022, we searched for studies that investigated whether point-of-care tests for any biomarker can be safely used to guide a primary care doctor's decision about prescribing antibiotics for someone with an ARI. We now have 13 studies in the updated review, with more than 10,500 participants. This is up from 6 trials, with 3300 participants, in the previous version.
Twelve of the included studies investigated point-of-care tests for the biomarker C‐reactive protein, and one investigated a test for the biomarker procalcitonin.
Starting with the evidence for the tests for C‐reactive protein. This shows that these tests reduce the number of patients given an antibiotic prescription, and that there are no differences in the number of recovered patients or the duration of the infection between the control group and the group managed with a CRP test. The number of satisfied patients was also similar between the two groups. Serious events such as hospitalization and death were very rare and firm conclusions are difficult to draw but we did not find any differences in these outcomes between the groups. This means that C‐reactive protein tests are probably effective and safe when used by doctors to guide the prescription of antibiotics in primary care, and new studies are unlikely to change this conclusion. However, more studies would still help if these were focused on children, immunocompromised individuals and people aged 80 years and older with comorbidities, because these groups are under-represented in the studies done to date.
Turning to the procalcitonin tests, because there was only one study, we cannot be confident about the effect on antibiotic use of using these tests in primary care. More studies are needed to assess their potential, and also to assess point‐of‐care tests for new biomarkers.
In conclusion, the findings of this updated review are important because reducing prescriptions of antibiotics in primary care settings would have a large impact on the total use of antibiotics, because the vast majority of antibiotic prescriptions are issued in these settings.

Mike: If you would like to consider the evidence in this review in more depth and watch for future updates if the new studies are done, it's available online. Just go to Cochrane Library dot com and search 'biomarker tests for ARI' to find it.