[From promising biomarker to useful test: a long and winding road].

The past few years have seen a tremendous acceleration in research on biomarkers. The vast majority of published research papers conclude with positive conclusions: gains are to be expected, improved outcomes for the patient and a more efficient and cheaper care process. Unfortunately, these promises are not always fulfilled. In this commentary, we discuss a recently proposed biomarker for impending pre-eclampsia: placental growth factor. Mean values of that marker have been shown to differ between women who developed pre-eclampsia and those who did not. Yet a randomized trial, published this year, showed that deploying that marker in clinical management did not improve maternal or neonatal outcomes. We discuss possible explanations and look forward to further research.