Determining Levels of Evidence and Formulating Conclusions

Table 1: Five levels of evidence

The levels of evidence used to summarize the findings are based on the levels of evidence developed by Sackett et al. (2000).  The levels proposed by Sackett et al. (2000) were modified to reduce the 10 categories from Sackett et al. (2000) to a less complex system from level 1 to level 5. For each level of evidence, we have provided additional descriptions specific to the types of research designs encountered in SCI rehabilitation to facilitate the decision-making process. 

For SCIRE versions 1.0 through 3.0 one randomized controlled trial (RCT) with a PEDro score > 6 was classified as an evidence level of 1. In response to a growing number of high-quality studies in various SCIRE chapters, the grading scheme has been modified for Version 4.0. The new grading scheme adds an additional dimension within the ‘level 1’ evidence category, which distinguishes between a single RCT with a PEDro score of > 6 (Level 1b) and 2 or more RCTs with PEDro scores of > 6 (Level 1a) (see Table 1).

The appropriateness of the control group was assessed per study.  In some studies, an able-bodied group may not have been an adequate control for the particular intervention used, but simply provided “normative’ values for comparison.  In those studies, the study was considered “not controlled” and the level of evidence reduced (e.g., level 4 pre-post). 

RCTs received priority when formulating conclusions. Conclusions were not difficult to form when the results of multiple studies were in agreement. However, interpretation became difficult when the study results conflicted. In cases where studies differed in terms of quality, the results of the study (or studies) with the higher quality score were more heavily weighted to arrive at the final conclusions. Sometimes, interpretation was difficult, for example, the authors needed to make a judgment when the results of a single study of higher quality conflicted with those of several studies of inferior quality. In these cases we attempted to provide a rationale for our decision and to make the process as transparent as possible.

As emphasized by Sackett et al. (1996), the evidence from systematic research should be integrated with clinical expertise and patients' choice to form best practice.