Summary

Biomarkers are important diagnostic tools that help physicians determine a patient's risk for developing a disease and can guide clinical decisions. However, at times, it is critical to understand if a specific biomarker causes disease or is merely reflective of the disease process. This distinction is important mainly if the biomarker is intended to be a therapeutic target (ie, lowering a biomarker with a drug with the hopes of lowering risk for disease). In humans, randomized controlled clinical trials and human genetics are two approaches to understand causal factors. This article discusses a human genetics approach—Mendelian randomization—to distinguish causal from noncausal biomarkers.