The need to treat mild hypertension. Misinterpretation of results from the Australian trial

J. D. Abernethy

Despite the clear-cut result of the Australian Therapeutic Trial in Mild Hypertension, which demonstrated prospectively the benefit of treatment of diastolic blood pressure in the range of 95 to 109 mm Hg, a retrospective analysis that classified subjects by the average diastolic pressure level attained during the trial purported to show an absence of treatment benefit at lower average diastolic pressures and a negative treatment effect at higher levels. However, the method of classification by average attained diastolic pressure introduced substantial selection bias, invalidating the retrospective analysis and rendering as spurious both the deleterious treatment effect and its lack of efficacy at lower diastolic levels.