Respiratory tract infection (RTI) is the fourth leading cause of mortality globally resulting in around three million deaths per annum, predominantly from pneumonia. In the West, whilst RTIs do not wreak the same toll that they do in the lower income countries, they are the most frequent reason for consulting a general practitioner (GP). The majority of RTIs affect the upper respiratory tract and are of viral origin; numerous studies conclude that there is no benefit in prescribing antimicrobials for an acute uncomplicated RTI. And as currently one of the most serious global healthcare concerns is antimicrobial resistance (AMR), it is imperative that diagnosis and treatment at primary care level do not augment this problem. Relevant national guidelines exist in most European countries, but there are considerable variations across the EU in the frequency that antimicrobials are prescribed for patients with RTIs, ranging from 28% in the Netherlands to 92% in Greece.
Point-of-care testing by GPs, however, can allow more prudent use of antimicrobials. GPs are being encouraged to measure C reactive protein (CRP), a very early marker of inflammation produced by the liver, as an adjunct to clinical examination. Serum levels increase within six hours of infection, peak within two to three days and decline rapidly to baseline level once the infection is resolved. Bacterial infections result in high levels >100 mg/L, whereas levels in viral infections rarely exceed 50 mg/L. And a cost-effective CRP POC test that can be performed within five minutes is available. Although serum procalcitonin level is more specific for distinguishing between bacterial and viral infections, the POC tests for this analyte currently take longer to obtain a result and are thus more suitable for hospital settings. The consensus from European consortia concerned with managing RTI patients and combating antimicrobial resistance is that patients with CRP levels <20 mg/L should not be prescribed antimicrobials, those with levels >100 mg/L should, and for those with levels in between signs, symptoms and risk factors should all be scrutinized and antimicrobials prescribed if symptoms worsen. This approach appears to be acceptable to both patients and GPs.
Randomized clinical trials have been carried out in several countries comparing