The biomarker paradigm: between diagnostic efficiency and clinical efficacy.

The interest in biomarker research has been growing exponentially, and this trend is not expected to reverse soon. Although the clinical usefulness of laboratory tests is conventionally defined in terms of diagnostic efficiency or clinical efficacy (or effectiveness), these notions are complementary but not interchangeable. The former concept is an expression of diagnostic accuracy but does not entail outcome assessment. Conversely, clinical efficacy investigates whether or not a certain test can produce significant changes in managed care and an improvement of clinical outcomes. The vast majority of published studies were mainly focused on diagnostic efficacy rather than on clinical efficacy, and this seems no longer sustainable in a world with limited resources. Although bridging the gap between efficiency and efficacy is not a trivial endeavour, a paradigm shift is necessary, wherein the laboratory community should focus on what clinicians need rather than pursuing an endless search for analytically perfect tests. In the foreseeable future, efficacy should be improved by translating this concept into a simple "six R" paradigm, namely, performing the Right test, with the Right method, at the Right time, to the Right patient, at the Right cost, for the Right outcome.