Table 1.

Guidelines of evidence synthesis^a

Level of evidence	Criteria of judgement
Strong	Provided by consistentb, statistically significant pooled results in SMD or OR derived from multiple RCTs, including at least two high-quality RCTsc
Moderate	Provided by statistically significant results in one high-quality RCTc or Provided by inconsistentb, statistically significant pooled results in SMD or OR derived from multiple RCTs, including at least one high-quality RCTc or Provided by consistentb, statistically significant pooled results in SMD or OR derived from multiple medium-quality RCTsc.
Limited	Provided by statistically significant results in one medium-quality RCTc or Provided by inconsistentb, statistically significant pooled results in SMD or OR derived from multiple RCTs, including at least one medium-quality RCTc or Provided by consistentb, statistically significant pooled results in SMD or OR derived from multiple low-quality RCTsc
Very limited	Provided by statistically significant results in one low-quality RCTc or Provided by inconsistentb, statistically significant pooled results in SMD or OR derived from multiple low-quality RCTsc
Conflicting	Provided by inconsistentb, statistically non-significant results in SMD or OR derived from multiple RCTs regardless of quality

RCT randomized controlled trial, SMD standard mean difference, OR odds ratio

^aEstablished in accordance with the “Best-evidence synthesis” which was adapted by Dorrestijn et al. [78] from the van Tulder’s criteria [79]

^bPooled results are considered consistent if no statistically significant heterogeneity (I², P > 0.05) been identified and those are considered inconsistent if statistically significant I² (P < 0.05) been identified

^cMethodological quality of a study is rated based on PEDro score as high (≥7/10), medium (4–6/10), and low (≤3/10)