Why do clinicians sometimes find it difficult to use the results of systematic reviews in routine clinical practice?

Reviews of systematic results have proved enormously useful in routine clinical practice. However, the uncritical application of the overall results of systematic reviews to clinical decisions about individual patients can sometimes do more harm than good. Clinical syndromes are often complex, with considerable pathological heterogeneity, and the likely balance of the risks and benefits of interventions can be difficult to judge on an individual patient basis. Active involvement of experienced clinicians is essential in the planning, reporting, and interpretation of reviews. Detailed consideration should be given to the possibility of diagnostic or pathological heterogeneity within the clinical trials included in the review or between the trial patients and patients seen in routine clinical practice. For treatments that have significant risk of harm or treatments that are particularly costly, meta-analysis of individual patient data with stratification by baseline risk is sometimes helpful in targeting treatment appropriately in routine clinical practice.