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 collapse the subcategories within a level (e.g., level 1a, 1b, 1c) into a single level.  This was performed to reduce the 10 categories from Sackett et al. (2000) to a less complex system from level 1 to level 5, as shown in table 1.  We provided additional descriptions specific to the types of research designs encountered in SCI rehabilitation to facilitate the decision-making process.  Sackett et al. (2000) distinguishes high and low quality randomized controlled trials (RCTs) into level 1b and level 2b, respectively.  To provide a more reliable decision-making process, we required that a level 1 RCT had a PEDro score of greater than or equal to 6 (good to excellent quality), while a level 2 RCT had a PEDro score of 5 or less.  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.