The utility of biomarkers in sorting out the complex patient.

Today's patients present with a complexity of illness far more significant than ever before. Risk factors, in particular for cardiovascular, renal, and metabolic diseases, often interact with each other at core pathophysiological levels. Biomarkers are inexpensive tools that may help differentiate disease states in complex patients. Ideal biomarkers are both sensitive and specific to the disease state being examined. Natriuretic peptides are the prototype of ideal biomarkers and are adjuncts for the diagnosis and exclusion of heart failure in the dyspneic patient, especially those presenting with comorbidities such as lung disease. Just as natriuretic peptide levels can be considered the arbiter of congestive heart failure, cardiac troponins are decisive for myocardial necrosis. Novel assays with higher sensitivity will aid in earlier diagnosis, albeit with some decreased specificity. Nevertheless, the patient presenting with comorbidities and atypical symptoms of myocardial infarction will not be arbitrarily sent home. In the future, other novel biomarkers, such as neutrophil gelatinase-associated lipocalin for acute kidney injury, may come to the forefront for diagnosis of disease in the complex patient.