The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [28]
Systems and challenges of grading evidence
Within the arena of evidence-based practice today, we must assess the quality of the evidence before it is used to inform practice. Hierarchies of evidence have been developed by a range of individuals and organizations in an attempt to identify the ‘best’ evidence to inform a particular decision that needs to be made in relation to a particular treatment, procedure or area of practice (Sackett et al. 2000). A key underlying assumption of using such a system is that not all evidence is equivalent (Rycroft-Malone 2006) and the quality of the evidence base therefore needs to be judged in some way. Making such judgements about evidence is complex and difficult to achieve. However, an explicit approach, as will be found in this manual, may help to facilitate critical appraisal of these judgements, provide confidence when applying evidence in practice and improve communication of this information (Grade Working Group 2004).
As Mantzoukas’ (2009) review of nursing research within the hierarchies of evidence recently outlined, one of the challenges for nursing is that many of the hierarchies of evidence do not consider some of the evidence bases discussed in this chapter and put a lower value on research evidence that is not a meta-analysis or cluster randomized controlled trial (CRCT). To address this problem, some writers such as Rolfe and Gardner (2006) have sought to challenge this and move from an ‘exclusive’ hierarchy to an ‘inclusive’ hierarchy that does not only consider evidence from research programmes but considers all sources of evidence together. How this is achieved is under discussion in the literature, so in the interim we have established, after much debate, a process to grade the procedures in this edition which captures all the evidence bases, not only the research.
Grading evidence in The Royal Marsden Hospital Manual of Clinical Nursing Procedures
The evidence underpinning all the procedures has been reviewed and updated. To reflect the current trends in EBP, the evidence presented to support the procedures within this edition of The Royal Marsden Hospital Manual of Clinical Nursing Procedures has been graded, with this grading made explicit to the reader. The rationale for the system adopted will now be outlined.
As we have seen, there are many sources of evidence and ways of grading evidence and this has led us to a decision to consider both of these factors when referencing the procedures. You will therefore see that references will identify if the source of the evidence was from:
clinical experience (Dougherty and Lamb 2008, E)
patient (Diamond 1998, P)
context and guidelines (DH 2010a, C)
research (Fellowes et al. 2004, R).
If there is no written evidence to support a clinical experience or guidelines as a justification for undertaking a procedure, the text will be referenced as an ‘E’ but will not be preceded by an author’s name.
For the evidence that comes from research, this referencing system will be taken one step further and the research will be graded using a hierarchy of evidence. The levels that have been chosen are adapted from Sackett et al. (2000) and can be found in Box 1.7.
Box 1.7 Levels of evidence
1a Systematic reviews of RCTs.
1b Individual RCTs with narrow confidence limits.
2a Systematic reviews of cohort studies.
2b Individual cohort studies and low-quality RCTs.
3a Systematic reviews of case–control studies.
3b Case–control studies.
5 Case series and poor-quality cohort and case–control studies.
6 Expert opinion.
RCTs, randomized controlled trials.
(Adapted from Sackett et al. 2000)
Taking the example above of Fellowes et al. (2004), this is a systematic review of RCTs from the Cochrane Centre and so would be identified in the references as: Fellowes et al. (2004, R1a).
Through this process we hope that the reader will be able to more clearly identify the nature of the evidence