Responders and non-responders to antihypertensive treatment.

Responders to antihypertensive treatment have been defined as any patient with a fall in mean arterial pressure, however small; any patient with a fall in mean arterial pressure of 5%, 10% or greater; and any patient achieving a goal blood pressure, usually a diastolic pressure less than 90 mm Hg. Non-responders are normally defined as those who do not fit into the category of a responder. Blood pressure, however, varies considerably during follow-up, and diastolic pressure has a within-subject standard deviation of 8 mm Hg. Blood pressure varies according to environmental factors such as temperature, diet and stress, and tends to drift downwards during follow-up as the patient becomes accustomed to having blood pressure taken, to the place of measurement and to the observer. In a statistical sense, responders may be defined as the 2.5% with a fall in DBP greater than 16 mm Hg, yet in clinical studies of a low sodium diet reports have indicated that 50% have experienced an increase in pressure and 50% a fall (responders). Although the characteristics of those with a fall in pressure are of interest and should be compared with those who do not respond, a 50:50 division is unlikely to help. Methods of identifying true responders and non-responders are discussed in this brief review, along with the errors that may arise from a misclassification and problems of conducting further trials of treatment on the non-responders.