What sort of evidence do we need in primary care?

[Extract] In this week's BMJ (p 635), Mant and colleagues raise again the question of whether large scale randomised controlled trials provide evidence relevant to primary care.1 In a cross sectional study they question whether the UK national clinical guidelines for stroke are applicable to primary care patients. These guidelines, largely based on the PROGRESS trial,1 recommend a target blood pressure of 140/85 mm Hg, with further lowering beyond this target desirable through use of a thiazide diuretic and an angiotensin converting enzyme inhibitor.