[Individual response to treatment: from Withering to contemporary medicine]

This is an essay dealing with the 1785 cohort study by William Withering (the "account"), in which he reported the results of the treatment with foxglove (Digitalis purpurea) in 163 patients suffering from various forms of hydropsy (water retention). Withering reported the results of all patients, and classified them into responders and non-responders. He identified the responders as suffering from heart failure. In the 18th century, medical treatments were judged as successful if they complied with the criteria a priori of the theory of the four humors, and not on the patient's response to the treatment. Withering was the first not only to compare the patient's conditions before and after treatment, but also to identify the individual clinical characteristics of the patients who responded. In modern medicine, drugs are released on the market and approved for use after what is known as "population-derived clinical research", principally randomized controlled trials, and guidelines. More than 200 years ago, Withering anticipated the current and growing trend towards individual responses to treatment, and personalized medicine.