Can inflammation tests help doctors decide whether to use antibiotics for respiratory tract infections?

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Key messages

1. When a patient presents with symptoms of respiratory tract infection in the doctor’s office, the doctor’s use of Point-of-care C-reactive protein testing during the visit probably reduces the number of patients prescribed antibiotics, without affecting the patient’s recovery.

2. We don’t know if point-of-care procalcitonin testing affect the use of antibiotics or the patient’s recovery.

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

What is point-of-care testing?

Point-of-care tests require only a few drops of blood and are performed during a consultation, providing results within 3-20 minutes. This means that blood samples not should be transported to a lab, and the 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 are inflammation and biomarkers?

Inflammation is a reaction in response to an injury such as a bacterial or viral infection. Your body naturally produces substances in response to inflammation that can be detected in the blood, called biomarkers. Point-of-care tests that detect biomarkers are often used when patients show signs of respiratory tract infection. Test results can tell doctors when not suspect a serious bacterial infection that requires 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 leukocytes.

What are antibiotics?

Antibiotics are drugs used to treat bacterial infections, and they are commonly used for respiratory tract infections. However, most respiratory tract infections are caused by viruses, such as the common cold, which antibiotics do not work against 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 decide on antibiotics?

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

What did we want to find out?

We wanted to find out if biomarkers as a point-of-care test used by primary care physicians can help decide whether or not to use antibiotics in people with respiratory tract infections.

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

What have we done?

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

We compared and summarized study results, and assessed our confidence in the evidence.

What did we find?

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

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

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

We do not know if procalcitonin testing has an effect on antibiotic prescriptions, recovery, hospitalizations, or risk of death.

What are the limits of the evidence?

We are moderately confident in the evidence for reduced antibiotic use with C-reactive protein testing. However, we are unconvinced of the evidence for a reduction in antibiotic use with procalcitonin, as we found only one study looking at the effect of procalcitonin in primary care.

Further studies are unlikely to change our conclusion regarding the effect of C-reactive protein use on antibiotic prescribing, but further studies are needed to assess the potential of the procalcitonin test at the point of service.

How up-to-date is this evidence?

The evidence is current to June 2022.

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