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

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)