Markers of acute inflammation in assessing and managing lower respiratory tract infections: focus on procalcitonin

This review describes the pathophysiological basis for using procalcitonin to help diagnose infections, and the strengths and weaknesses of implementing the test rationally in a routine clinical setting. Meta-analyses of observational studies and intervention studies both suggest that as a surrogate marker, procalcitonin allows an improved diagnostic assessment of a variety of infections, e.g., respiratory tract infections, meningitis, acute infectious endocarditis and pancreatitis. Measuring procalcitonin is not a substitute for careful clinical assessment and obtaining appropriate cultures in all patients. However, used appropriately, procalcitonin allows an earlier diagnosis of infection and can inform physicians about the course and prognosis of the disease better than more commonly used clinical and laboratory markers. With use of a sensitive assay, a procalcitonin-based therapeutic strategy can safely and markedly reduce antibiotic usage in those respiratory tract infections that are mostly viral, and in viral meningitis. More sensitive procalcitonin assays, with a functional sensitivity within the normal reference range of >0.03 microg/L, should be available soon. There is a need for more intervention studies in other sites of infection to tackle the existing vicious cycle of antibiotic overuse and emerging multiresistance. Furthermore, as procalcitonin is a hormokine mediator, its immunoneutralisation might open new treatment options for sepsis.