Systematic reviews: gatekeepers of nursing knowledge.

The past few decades have seen a considerable increase in the number of available health care products and interventions. This growth has been matched by a similar expansion in the health care literature. As a result of these factors, the demand for evidence to support practice is growing, but finding the best evidence is becoming increasingly difficult. In response, the use of systematic reviews is increasing and they are starting to replace the primary research as the basis for health care decisions. To date, these reviews have focused predominantly on effectiveness and so have been limited to randomized controlled trials. As a result of this, the interpretive, observational and descriptive research methods that are utilized by nursing have commonly been either excluded from the review or are classified as 'low level' evidence. To address this, nursing must participate in the development of systematic review methods that better answer the questions posed by the profession.