The whole point of appraisal is to determine how reliable that evidence is and to identify any flaws and bias likely to affect the outcome. A great deal of the research around pharmacy services is observational in style. Experience of writing systematic reviews around pain interventions has shown that while randomised controlled trials are excellent evidence for effect, they are not so good at revealing adverse or unwanted effects. A disease that is independent of underlying disease and results from either the drug administration, medical or surgical acts for prophylaxis, diagnosis or other therapy. Economic analyses are being demanded yet can be very difficult to interpret. It is important to have mechanisms in place to assess harmful effects so that treatments that do more harm than good can be identified. Decision tree analysis is a method of plotting out potential and real solutions to problems of a complex nature.