Genetic variation in hypertensive and 'control' strains. What are we controlling for anyway?

The problem of proper "controls" has been a topic of central interest to researchers in clinical and experimental hypertension for many years. In this issue of Hypertension, two groups of investigators examine this question using DNA typing techniques,with regard to the comparability of commonly used genetically hypertensive rat strains and their normotensive controls. Confirming earlier data in a more quantitative fashion, the authors point out widespread sequence dissimilarities between sets of hypertensive and control strains. Because of their potential impact on almost any area of biomedical research, these reports deserve critical examination of their true implications and relevance.