Biomarkers and Pneumonia: Should We All be Using Them?

Community-acquired pneumonia (CAP) is a serious health problem worldwide with an annual incidence of 0.3%-0.5% in the adult population. Moreover, CAP continues to be the leading cause of death from infectious diseases. This justifies the interest in studying all clinical aspects relating to CAP. A new approach is to evaluate biological markers of infection and inflammation as an expression of the host's inflammatory response against the microorganism, in order to obtain diagnosis, aetiology, prognosis and treatment information. The most frequently studied biomarkers are C-reactive protein (CRP), procalcitonin (PCT) and cytokines; other biomarkers are currently obtaining promising results. Although not uniformly, most authors conclude that biomarkers can help in the diagnosis of CAP, few studies analyse the capacity of biomarkers to identify the potential causative agent and the best results have been established children. Linked with this, biomarkers (mainly PCT) have been successfully used to guide prescription of antibiotics in patients with suspected CAP. Treatment guided by serum PCT was a safe way to avoid antibiotics, although economic savings were overshadowed by PCT analysis costs. Approximately 10%-15% of patients hospitalized for CAP develop treatment failure and almost 6% may manifest rapidly progressive pneumonia; serum levels of biomarkers have been shown to identify patients at risk of treatment failure and may therefore guide treatment management. Clinical data scoring systems have been recognized as useful tools to assess the stability and outcome of patients with CAP. Analysis of systemic biomarkers in addition to clinical scores has been shown to improve both prediction of the absence of severe complications and 30- day mortality as predicted by the PSI or CURB65/CRB65 scales. Data from the literature appears to support the use of biomarkers in routine clinical practice when CAP is suspected.