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Table 2 The item-based comparison on the quality of registered (or with a prior protocol) DRMAs and matched controls

From: Protocol registration or development may benefit the design, conduct and reporting of dose-response meta-analysis: empirical evidence from a literature survey

Quality Checklist Registered Matched control Rate difference P value
Modified AMSTAR
 Item 1: Was there duplicate study selection? 22/45 40/90 0.04 (− 0.13, 0.22) 0.63
 Item 2: Was there duplicate data extraction? 40/45 65/90 0.17 (0.04, 0.30) 0.01
 Item 3: Was there at least two database searched? 39/45 77/90 0.01 (− 0.11, 0.13) 0.86
 Item 4: Was there any search strategy documented? 30/45 30/90 0.33 (0.17, 0.50) < 0.01
 Item 5: Was the status of publication used as an inclusion criterion? 18/45 27/90 0.10 (−0.07, 0.27) 0.25
 Item 6: Was a list of studies of included provided? 43/45 90/90 −0.04 (− 0.11, 0.02) 0.20
 Item 7: Was a list of studies of excluded provided? 20/45 21/90 0.21 (0.04, 0.38) 0.02
 Item 8: Were the characteristics of the included studies provided? 45/45 89/90 0.01 (−0.03, 0.05) 0.59
 Item 9: Was the scientific quality of the included studies assessed? 22/45 50/90 −0.07 (− 0.25, 0.11) 0.46
 Item 10: Was the scientific quality of the included studies documented (only provide total score should be avoided)? 13/45 28/90 −0.02 (− 0.19. 0.14) 0.79
 Item 11: Was the scientific quality of the included studies used appropriately in formulating conclusions? 5/45 9/90 0.01 (−0.10, 0.12) 0.84
 Item 12: Were the methods used to combine the findings (dose-response) of studies appropriate? 41/45 84/90 −0.02 (− 0.12, 0.08) 0.66
 Item 13: Was the likelihood of publication bias assessed? 45/45 80/90 0.11 (0.04, 0.18) < 0.01
 Item 14: Was the conflict of interest stated? 43/45 80/90 0.07 (−0.02. 0.16) 0.14
Modified PRISMA
 Item 1 (Title): Identify the report as a systematic review, meta-analysis, or both. 45/45 90/90 0.00 (−0.03, 0.03) ≈ 1
 Item 2 (Introduction): Describe the rationale for the review in the context of what is already known. 45/45 90/90 0.00 (−0.03, 0.03) ≈ 1
 Item 3 (Introduction): Provide an explicit objective(s) with reference to PICOS principle. 45/45 90/90 0.00 (−0.03, 0.03) ≈ 1
 Item 4 (Methods): Specify criteria for eligibility, giving rationale. 43/45 87/90 −0.01 (− 0.08, 0.06) 0.76
 Item 5 (Methods): Describe all information sources (e.g. databases) in the search and date last searched. 45/45 90/90 0.00 (−0.03, 0.03) ≈ 1
 Item 6 (Methods): Present full electronic search strategy for at least one database. 36/45 32/90 0.44 (0.29, 0.60) < 0.01
 Item 7 (Methods): State the process for selecting studies (two stage: title and abstract screen, then the full text). 15/45 21/90 0.10 (−0.06, 0.26) 0.23
 Item 8 (Methods): Describe method of data extraction and any processes for obtaining and confirming data. 40/45 71/90 0.10 (−0.03, 0.23) 0.12
 Item 9 (Methods): List and define all variables for which data were sought and any assumptions made. 41/45 82/90 0.00 (−0.10, 0.10) ≈ 1
 Item 10 (Methods): Describe methods used for assessing risk of bias of individual studies. 26/45 56/90 −0.04 (− 0.22, 0.13) 0.62
 Item 11 (Methods): State the principal summary measures (e.g., risk ratio, difference in means). 43/45 80/90 0.07 (−0.02, 0.16) 0.14
 Item 12 (Methods): Describe the methods of handling data and combining results of studies. 45/45 90/90 0.00 (−0.03, 0.03) ≈ 1
 Item 13 (Methods): Specify any assessment of risk of bias for the pooled evidence (e.g. publication bias). 45/45 83/90 0.08 (0.01, 0.14) 0.02
 Item 14 (Methods): Describe methods of additional analyses (e.g. sensitivity analysis, meta-regression). 45/45 86/90 0.04 (−0.01, 0.10) 0.11
 Item 15 (Results): Give numbers of studies screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally with a flow diagram. 41/45 83/90 −0.01 (− 0.11, 0.09) 0.83
 Item 16 (Results): For each study, present characteristics for which data were extracted. 44/45 90/90 −0.02 (− 0.08, 0.03) 0.42
 Item 17 (Results): Present data on risk of bias of within each study (study level). 22/45 45/90 −0.01 (− 0.19, 0.17) 0.90
 Item 18 (Results): Present summery data, effect estimates and confidence intervals for each study. 45/45 88/90 0.02 (−0.02, 0.07) 0.34
 Item 19 (Results): Present results of each meta-analysis, with confidence intervals and measures of consistency. 45/45 90/90 0.00 (−0.03, 0.03) ≈ 1
 Item 20 (Results): Present results of risk of bias across studies (publication bias, outcome level). 45/45 80/90 0.11 (0.04, 0.18) < 0.01
 Item 21 (Results): Give results of additional analyses, if done. 45/45 87/90 0.03 (−0.02, 0.08) 0.20
 Item 22 (Discussion): Summarize the main findings including the strength of evidence for each main outcome. 45/45 88/90 0.02 (−0.02, 0.07) 0.34
 Item 23 (Discussion): Discuss limitations at study and outcome level 44/45 80/90 0.09 (0.01, 0.17) 0.03
 Item 24 (Discussion): Provide a general interpretation of the results and implications for future research. 45/45 90/90 0.00 (−0.03, 0.03) ≈ 1
 Item 25 (Funding): Describe sources of funding and other support for the systematic review. 43/45 70/90 0.18 (0.07, 0.28) < 0.01
  1. Rate difference was the absolute difference of the adherence rate of the two groups, and the statistical inference was conducted by t test. Those in bold were statistically significant (p < 0.05)