Effectiveness of Biomarkers in Cardiology

Assessment of a biomarker’s effectiveness should include two sequential criteria. First, the biomarker should add prognostic value in relation to basic clinical and laboratory data. Second, the information provided by the biomarker should promote changes in medical conduct in a way that ultimately benefits the patient. Beginning with the analysis of prognostic value, a new biomarker must have a prognostic value independent of conventional risk markers. However, this criterion of statistical significance is not enough to guarantee clinical significance. Once the statistical significance is confirmed by multivariate analysis, it is necessary to proceed and evaluate whether the biomarker increases our ability to identify individuals who will present the undesirable outcome. This is done by incremental analysis of the C-statistic and net reclassification analysis1. For example, although high sensitivity C-reactive protein has an independent association with cardiovascular risk, it only slightly increases the discriminatory capacity in Framingham score2. The coronary calcium score, on the other hand, can increase the C-statistic of Framingham score, in addition to correctly reclassifying a proportion of patients3. This incremental value is an essential condition for a biomarker to be effective, because only then can its result correctly modify clinical decisions.