Blood test could avoid inappropriate use of antibiotics for respiratory infections

A rapid blood test to help distinguish between bacterial and other (predominantly viral) infections could substantially reduce the inappropriate use of antibiotics for common infections, conclude authors of a study in this week’s issue of THE LANCET.

Lower respiratory tract infections are often treated with antibiotics-even though there is often no evidence of bacterial infection. Such inappropriate use of antibiotics is contributing to the increase of antibiotic-resistant bacteria with serious implications for public health. Blood concentrations of a calcitonin precursor protein known as procalcitonin are substantially raised during acute bacterial infection.

Beat Müller from University Hospital Basel, Switzerland, and colleagues assessed the effectiveness of a sensitive blood test to identify procalcitonin concentrations to guide antibiotic treatment among patients with lower respiratory-tract disease (eg, pneumonia, bronchitis).

243 patients with suspected lower respiratory tract infections were randomly assigned standard care (standard group) or procalcitonin-guided treatment (procalcitonin group). Antibiotics were given only if procalcitonin concentrations were above a specific threshold among patients in the procalcitonin group.

The number of patients in the procalcitonin group who received antibiotics was halved compared with the standard treatment group. This withholding of antibiotics had no adverse effect on health outcome (no overall difference between the two groups, with 97% of all patients making a good recovery). Around 80% of patients were later found to have viral infection for diagnoses such as pneumonia (36% of patients), exacerbation of chronic obstructive pulmonary disease (COPD, 25%), and acute bronchitis (24%). Conversely, in patients with acute exacerbation of COPD, 60% positive sputum cultures for bacteria were found regardless of whether procalcitonin concentrations were high or low; however, those patients not treated with antibiotics because of low procalcitonin still had successful infection clearance: these patients were colonised with bacteria, but the bacteria were not responsible for the infection.

Beat Müller comments: ‘Procalcitonin guidance substantially reduced antibiotic use in lower respiratory tract infections. Withholding antimicrobial treatment did not compromise outcome. In view of the current overuse of antimicrobial therapy in often self-limiting acute respiratory tract infections, treatment based on procalcitonin measurement could have important clinical and financial implications’.