Biomarkers as point-of-care tests to guide prescription of antibiotics in people with acute respiratory infections in primary care

Background: Acute respiratory infections (ARIs) are by far the most common reason for prescribing an antibiotic in primary care, even though the majority of ARIs are of viral or non-severe bacterial aetiology. It follows that in many cases antibiotic use will not be beneficial to a patient's recovery but may expose them to potential side effects. Furthermore, limiting unnecessary antibiotic use is a key factor in controlling antibiotic resistance. One strategy to reduce antibiotic use in primary care is point-of-care biomarkers. A point-of-care biomarker (test) of inflammation identifies part of the acute phase response to tissue injury regardless of the aetiology (infection, trauma, or inflammation) and may be used as a surrogate marker of infection, potentially assisting the physician in the clinical decision whether to use an antibiotic to treat ARIs. Biomarkers may guide antibiotic prescription by ruling out a serious bacterial infection and help identify patients in whom no benefit from antibiotic treatment can be anticipated. This is an update of a Cochrane Review first published in 2014.

Objectives: To assess the benefits and harms of point-of-care biomarker tests of inflammation to guide antibiotic treatment in people presenting with symptoms of acute respiratory infections in primary care settings regardless of patient age.

Search methods: We searched CENTRAL (2022, Issue 6), MEDLINE (1946 to 14 June 2022), Embase (1974 to 14 June 2022), CINAHL (1981 to 14 June 2022), Web of Science (1955 to 14 June 2022), and LILACS (1982 to 14 June 2022). We also searched three trial registries (10 December 2021) for completed and ongoing trials.

Selection criteria: We included randomised controlled trials (RCTs) in primary care patients with ARIs that compared the use of point-of-care biomarkers with standard care. We included trials that randomised individual participants, as well as trials that randomised clusters of patients (cluster-RCTs).

Data collection and analysis: Two review authors independently extracted data on the following primary outcomes: number of participants given an antibiotic prescription at index consultation and within 28 days follow-up; participant recovery within seven days follow-up; and total mortality within 28 days follow-up. We assessed risk of bias using the Cochrane risk of bias tool and the certainty of the evidence using GRADE. We used random-effects meta-analyses when feasible. We further analysed results with considerable heterogeneity in prespecified subgroups of individual and cluster-RCTs.

Main results: We included seven new trials in this update, for a total of 13 included trials. Twelve trials (10,218 participants in total, 2335 of which were children) evaluated a C-reactive protein point-of-care test, and one trial (317 adult participants) evaluated a procalcitonin point-of-care test. The studies were conducted in Europe, Russia, and Asia. Overall, the included trials had a low or unclear risk of bias. However all studies were open-labelled, thereby introducing high risk of bias due to lack of blinding. The use of C-reactive protein point-of-care tests to guide antibiotic prescription likely reduces the number of participants given an antibiotic prescription, from 516 prescriptions of antibiotics per 1000 participants in the control group to 397 prescriptions of antibiotics per 1000 participants in the intervention group (risk ratio (RR) 0.77, 95% confidence interval (CI) 0.69 to 0.86; 12 trials, 10,218 participants; I² = 79%; moderate-certainty evidence). Overall, use of C-reactive protein tests also reduce the number of participants given an antibiotic prescription within 28 days follow-up (664 prescriptions of antibiotics per 1000 participants in the control group versus 538 prescriptions of antibiotics per 1000 participants in the intervention group) (RR 0.81, 95% CI 0.76 to 0.86; 7 trials, 5091 participants; I² = 29; high-certainty evidence). The prescription of antibiotics as guided by C-reactive protein tests likely does not reduce the number of participants recovered, within seven or 28 days follow-up (567 participants recovered within seven days follow-up per 1000 participants in the control group versus 584 participants recovered within seven days follow-up per 1000 participants in the intervention group) (recovery within seven days follow-up: RR 1.03, 95% CI 0.96 to 1.12; I² = 0%; moderate-certainty evidence) (recovery within 28 days follow-up: RR 1.02, 95% CI 0.79 to 1.32; I² = 0%; moderate-certainty evidence). The use of C-reactive protein tests may not increase total mortality within 28 days follow-up, from 1 death per 1000 participants in the control group to 0 deaths per 1000 participants in the intervention group (RR 0.53, 95% CI 0.10 to 2.92; I² = 0%; low-certainty evidence). We are uncertain as to whether procalcitonin affects any of the primary or secondary outcomes because there were few participants, thereby limiting the certainty of evidence. We assessed the certainty of the evidence as moderate to high according to GRADE for the primary outcomes for C-reactive protein test, except for mortality, as there were very few deaths, thereby limiting the certainty of the evidence.

Authors' conclusions: The use of C-reactive protein point-of-care tests as an adjunct to standard care likely reduces the number of participants given an antibiotic prescription in primary care patients who present with symptoms of acute respiratory infection. The use of C-reactive protein point-of-care tests likely does not affect recovery rates. It is unlikely that further research will substantially change our conclusion regarding the reduction in number of participants given an antibiotic prescription, although the size of the estimated effect may change. The use of C-reactive protein point-of-care tests may not increase mortality within 28 days follow-up, but there were very few events. Studies that recorded deaths and hospital admissions were performed in children from low- and middle-income countries and older adults with comorbidities. Future studies should focus on children, immunocompromised individuals, and people aged 80 years and above with comorbidities. More studies evaluating procalcitonin and potential new biomarkers as point-of-care tests used in primary care to guide antibiotic prescription are needed. Furthermore, studies are needed to validate C-reactive protein decision algorithms, with a specific focus on potential age group differences.