The publication of Clinical Evidence is a major event in the process of assisting clinicians in making their practices evidence based. Its aims are precise: to provide evidence to assist clinicians in answering the questions most relevant to clinical practice and to highlight areas where that evidence is lacking. The book does not aim to make recommendations, nor does it judge effectiveness or cost-effectiveness. Both beneficial and harmful effects of therapy are presented, but clinicians are left to translate these effects into an estimate of effectiveness for the individual patient.

An explicit and multilayered approach was used in the systematic retrieval and appraisal of the evidence …