Abstract: The only point-of-care biomarker of infection currently available to primary care identified in this review was C-reactive protein. We included six trials (3284 participants; 139 children) that evaluated a C-reactive protein point-of-care test. The available information was from trials with a low to moderate risk of bias that address the main objectives of this review. Overall a reduction in the use of antibiotic treatments was found in the C-reactive protein group (631/1685) versus standard of care (785/1599). However, the high level of heterogeneity and the statistically significant test for subgroup differences between the three RCTs and three cluster-RCTs suggest that the results of the meta-analysis on antibiotic use should be interpreted with caution and the pooled effect estimate (risk ratio (RR) 0.78, 95% confidence interval (CI) 0.66 to 0.92; I2 statistic = 68%) may not be meaningful. The observed heterogeneity disappeared in our preplanned subgroup analysis based on study design: RR 0.90, 95% CI 0.80 to 1.02; I2 statistic = 5% for RCTs and RR 0.68, 95% CI 0.61 to 0.75; I2 statistic = 0% for cluster-RCTs, suggesting that this was the cause of the observed heterogeneity. There was no difference between using a C-reactive protein point-of-care test and standard care in clinical recovery (defined as at least substantial improvement at day 7 and 28 or need for re-consultations day 28). However, we noted an increase in hospitalisations in the C-reactive protein group in one study, but this was based on few events and may be a chance finding. No deaths were reported in any of the included studies. We classified the quality of the evidence as moderate according to GRADE due to imprecision of the main effect estimate. A point-of-care biomarker (e.g. C-reactive protein) to guide antibiotic treatment of ARIs in primary care can reduce antibiotic use, although the degree of reduction remains uncertain. Used as an adjunct to a doctor's clinical examination this reduction in antibiotic use did not affect patient-reported outcomes, including recovery from and duration of illness. However, a possible increase in hospitalisations is of concern. A more precise effect estimate is needed to assess the costs of the intervention and compare the use of a point-of-care biomarker to other antibiotic-saving strategies.

Plain-language summary: We included six studies with a total of 3284 participants with ARIs from primary care settings (point-of care test: C-reactive protein). Two of the included studies received direct financial support from manufacturers. The evidence is current to January 2014. The only point-of-care biomarker of infection currently available to primary care identified in the review was C-reactive protein. A reduction in antibiotic use is likely to be achieved by a C-reactive protein point-of-care test but due to differences in the designs of the included studies, it was not possible to obtain a precise effect estimate of the reduction. There were no deaths in the studies and we did not find evidence suggesting that time to recovery from ARIs and their duration were longer, nor that levels of patient satisfaction or number of re-consultations were affected in the C-reactive protein group. However, a possible increase in the risk of hospital admission cannot be ruled out. We ranked the evidence as of moderate quality according to the GRADE levels due to an imprecise effect estimation. Used as an adjunct to a doctor's clinical examination point-of-care tests (e.g. C-reactive protein) can reduce antibiotic use in ARIs in general practice. The possibility of an increased risk of hospital admission suggests that care must be taken in how these tests are used. A more precise effect estimate is needed to assess the costs of the intervention and compare the use of a point-of-care biomarker to other antibiotic-saving strategies.