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Table 1 Characteristics of the reviews and provided information about the included primary studies

From: Overview of data-synthesis in systematic reviews of studies on outcome prediction models

     n = 50 reviews
Item: Description of item:    Yes No Unclear Not applicable
     N % N % N % N %
Section 1: Information about the objective and design of the reviews         
1. Type of primary studies included n = 50 (%)         
   Only outcome prediction models 14 (28.0)         
   Combination of prognostic factor & outcome prediction studies 3 (6.0)         
   Unclear 33 (66.0)         
2. Is the outcome of interest clearly described?    47 (94.0) 1 (2.0) 2 (4.0)   
3. Is information about quality assessment provided?    36 (72.0) 14 (28.0)     
3a. Method used           
   Methodological criteria list 3 (6.0)         
   Individual items 2 (4.0)         
   Not applicable 14 (28.0)         
   Methodological criteria & study design 31 (62.0)         
4. Was study quality accounted for    21 (42.0) 13 (26.0) 2 (4.0) 14 (28.0)
4a. Method used *# n = 23 (%)         
   Exclusion of poor quality studies (cut-off score used) 3 (13.0)         
   Sensitivity analysis based on total quality score 5 (21.7)         
   Levels of evidence 12 52.2)         
   Subgroup analysis 7 (30.4)         
   Study findings weighted for quality 3 (13.0)         
   Other 2 (8.7)         
Section 2: Information about the design and results of the primary studies         
5. Outcomes clearly described 36 (72.0) 20 (20.0) 4 (8.0)   
6. Statistical methods used for variable selection described 2 (4.0) 46 (92.0) 2 (4.0)   
7. Treatments described 6 (12.0) 37 (74.0) 7 (14.0)   
8. Univariable point estimates for all the variables of the primary studies are provided 5 (10.0) 42 (84.0) 3 (6.0)   
8a. Univariable estimates for dispersion for all the variables of the primary studies are provided 5 (10.0) 42 (84.0) 3 (6.0)   
9. All variables (starting predictors) used to develop a model are described 4 (8.0) 36 (72.0) 10 (20.0)   
10. Multivariable point estimates for each predictor in the final outcome prediction model are provided 11 (22.0) 33 (66.0) 4 (8.0) 2 (4.0)
10a. Multivariable estimate of dispersion provided for each predictor in the final outcome prediction model 11 (22.0) 33 (66.0) 4 (8.0) 2 (4.0)
11. Model performance is assessed and described 7 (14.0) 38 (76.0) 2 (4.0) 3 (6.0)
12. number of events per variable is described 4 (8.0) 44 (88.0) 2 (4.0)   
Section 3: Data-analysis and synthesis in the reviews         
13. Heterogeneity between studies described 45 (90.0) 4 (8.0) 1 (2.0)   
14. Qualitative data-synthesis presented 49 (98.0) 1 (2.0)     
14a. Method used n = 49 (%)         
   Statistical significance 22 (44.9)         
   Consistency of findings 7 (14.3)         
   Consistency of findings & statistical significance 6 (12.2)         
   Available method of defining levels of evidence 3 (6.1)         
   Consistency of findings & levels of evidence 3 (6.1)         
   other combinations 8 (16.3)         
15. Quantitative analysis performed    10 (20.0) 40 (80.0)     
15a. Method used n = 10 (%)         
   Random effects model 4 (40.0)         
   Fixed effects model 1 (10.0)         
   Random & Fixed effects model 3 (30.0)         
   Other 2 (20.0)         
     n = 10 reviews
15b. Statistical heterogeneity assessed    4 (40.0) 6 (60.0)     
15c. Method used to assess statistical heterogeneity n = 4 (%)         
   I2 2 (50.0)         
   I2 & Chi2 1 (25.0)         
   Other 1 (25.0)         
     n = 50 reviews
16. Graphic presentation of results provided    8 (16.0) 42 (84.0)     
16a. Method used n = 8 (%)         
   Forest plot 6 (75.0)         
   Forest plot & scatter plot 1 (12.5)         
   Barplot 1 (12.5)         
17. Sensitivity analysis performed    6 (12.0) 43 (86.0) 1 (2.0)   
17a. Method used n = 6 (%)         
   Different cut-offs for study quality 3 (50.0)         
   Methodological criteria 1 (16.7)         
   Methodological criteria & weights for quality 1 (16.7)         
   Including other (excluded) cohorts 1 (16.7)         
  1. * includes ‘yes’ and ‘unclear’ categories.
  2. # numbers and percentages may add up to more than 23 and 100%, due to multiple methods in some reviews.