What cardiologists do need to know about procalcitonin

This review will highlight the potential application of procalcitonin, a novel marker of systemic bacterial infection, in two clinical settings relevant to cardiologists: infective endocarditis (IE) and lower respiratory tract infections (LRTI): The variability in the clinical presentation of infective endocarditis (IE) makes the diagnosis a clinical challenge. However, rapid diagnosis and initiation of effective treatment are essential to good patient outcome. Serum calcitonin precursor levels, including procalcitonin, are elevated in systemic bacterial infections and seem to be helpful in the diagnosis of IE. The utility of procalcitonin in clinical practice was examined in a prospective cohort of patients with the suspicion of IE. Procalcitonin was significantly higher in patients with IE (median 6.56 microg/L) as compared with patients with other final diagnoses (median 0.44 microg/L, p < 0.001). The area under the ROC curve using procalcitonin to predict infective endocarditis was 0.856, as compared to 0.657 for C-reactive protein. The optimum concentration of procalcitonin for the calculation of positive and negative predictive accuracy as obtained from the ROC curve was 2.3 microg/L. Using this cut-off, the test characteristics of procalcitonin were as follows: sensitivity 81%, specificity 85%, negative predictive value 92%, positive predictive value 72%. Although most LRTIs are due to viral infections, they are very often treated with antibiotics. This excessive use of antibiotics is believed to be the main cause of the spread of antibiotic-resistant bacteria. A procalcitonin-based therapeutic strategy has shown to reduce antibiotic usage in LRTI. Based upon serum procalcitonin levels, the use of antibiotics was more or less discouraged (<0.1 or <0.25 microg/L) or encouraged (> or =0.5 or > or =0.25 microg/L), respectively. Final diagnoses included pneumonia (36%), acute exacerbation of COPD (25%), and acute bronchitis (24%). Clinical and laboratory outcome was similar in both groups and favourable in 96.7%. In the procalcitonin group, the adjusted relative risk of antibiotic exposure was 0.49 (p < 0.001), as compared to the standard group. Thus, using a sensitive assay, procalcitonin-guidance substantially and safely reduced antibiotic usage in LRTI.