Cardiovascular investigations often involve ratio-based metrics or differences: ejection fraction, arterial pressure augmentation index, coronary fractional flow reserve, pulse pressure. Focusing on a single number (ratio or difference) implies that information is lost. The lost companions constitute a well-defined but thus far unrecognized class, having additive value, a physical dimension, and often a physiological meaning. Physiologists should play a prominent role in exploring these complementary avenues and also define alternatives.
Kerkhof, P. L. M., Peace, R. A., & Handly, N. (2019). Ratiology and a Complementary Class of Metrics for Cardiovascular Investigations. Physiology, 34(4), 250-263. https://doi.org/10.1152/physiol.00056.2018