Key messages 

1. When a patient presents with symptoms of an airway infection at the doctor's office, the doctor's use of C-reactive protein point-of-care tests during the visit probably reduces the number of patients given an antibiotic prescription, without affecting patient recovery.

2. We do not know if procalcitonin point-of-care tests have an effect on antibiotic use or patient recovery.

3. Future studies should focus on children, people with diseases of the immune system, and people aged 80 years and above with comorbidities (additional medical conditions). Studies evaluating procalcitonin and new biomarkers to guide antibiotic prescription are recommended. 

What are point-of-care tests?

Point-of-care tests need only a few drops of blood and are taken during a consultation, providing results within 3 to 20 minutes. This means that blood samples do not need to be transported to a laboratory, and results can be used immediately to make treatment choices during a visit to the doctor. There are point-of-care tests that can detect different substances in the blood that your body produces in response to inflammation. These substances are called biomarkers. 

What is inflammation and biomarkers?

Inflammation is a reaction in response to injury such as bacterial or viral infections. Your body naturally produces substances in response to inflammation that can be detected in the blood, which are known as biomarkers. Point-of-care tests that detect biomarkers are often used when patients have signs of an airway infection. Test results can inform doctors when not to suspect a serious bacterial infection that needs antibiotic treatment to prevent serious illness and possibly death. There are currently three types of biomarkers available as point-of-care tests: C-reactive protein, procalcitonin, and leucocytes.

What are antibiotics?

Antibiotics are medications used to treat bacterial infections, and they are commonly used for airway infections. However, most airway infections are caused by viruses, such as the common cold, against which antibiotics do not work, and can cause harm. Overuse can lead to antibiotic resistance, which means that antibiotics lose their effectiveness and may no longer be effective against serious infections.  

Why do we need to investigate whether tests help doctors to decide on antibiotics?

No test can provide absolute certainty regarding when to use antibiotics, but correctly used biomarkers could help doctors make the right decision about when to prescribe antibiotics. We investigated if biomarkers as point-of-care tests help doctors reduce antibiotic prescriptions. 

What did we want to find out?

We wanted to know whether biomarkers as a point-of-care test used by primary care doctors can help decide whether to use antibiotics in people with airway infections.

We were interested in the effect of biomarker guidance on the number of prescriptions of antibiotics, patient recovery, hospital admissions, and risk of death.

What did we do?

We searched for studies that investigated whether biomarkers used as point-of-care tests in primary care can be safely used to guide a doctor's decision whether to prescribe antibiotics.

We compared and summarised results of the studies, and rated our confidence of the evidence.

What did we find?

We found 13 studies with a total of 10,535 participants who had symptoms of airway infections and who saw a doctor in a primary care setting for possible treatment. 

Twelve studies investigated tests for the biomarker C-reactive protein, and one study investigated a test for the biomarker procalcitonin. 

Use of tests for C-reactive protein probably reduces the number of patients given an antibiotic prescription, but differences in study design and where the studies took place meant that the precise effect is uncertain. Using these tests probably does not affect the number of patients that recover, and may not reduce the number of patients that feel satisfied with their treatment. C-reactive protein tests may not lead to an increase in deaths. This means the tests are probably safe when used to guide the prescription of antibiotics.

We do not know if procalcitonin tests have an effect on prescriptions of antibiotics, recovery, hospital admissions, or risk of death.

What are the limitations of the evidence?

We are moderately confident in the evidence for a reduction in antibiotics use with C-reactive protein tests. However, we are not confident in the evidence for a reduction in antibiotics use with procalcitonin, as we only found one study investigating the effect of procalcitonin in primary care. 

New studies are unlikely to change our conclusion regarding the effect of the use of C-reactive protein on prescribing antibiotics, but more studies are needed to assess the potential for the procalcitonin point-of-care test. 

How up-to-date is this evidence?

The evidence is current to June 2022.