Table 1

Items identified through the factor analysis

Original instrument (item no)

1 Protocol

Sacks

.58

2 Literature Search

Sacks

.82

3 List of Trials Analyzed

Sacks

.75

4 Log of Rejected Trials

Sacks

.68

5 Treatment Assignment

Sacks

.80

6 Ranges of Patients

Sacks

7 Range of Treatment

Sacks

.88

8 Range of Diagnosis

Sacks

.80

9 CombinabilityCriteria

Sacks

.88

10 Measurement

Sacks

.57

11 Selection Bias

Sacks

.85

12 Data abstraction

Sacks

.50

13 Inter-observer Agreement

Sacks

.65

14 Sources of Support

Sacks

.64

15 Statistical Methods

Sacks

.81

16. Statistical Errors

Sacks

17 Confidence Intervals

Sacks

.73

18 Subgroup Analysis

Sacks

19 Quality Assessment

Sacks

.77

20 Varying Methods

Sacks

.63

21 Publication Bias 1

Sacks

.77

22 Caveats

Sacks

23 Economic Impact

Sacks

.84

24 Language 1

Added to Sacks

.79

25 Search Strategy

OQAQ (1)

.81

26 Was the search comprehensive

OQAQ (2)

27 Criteria used for deciding which studies to include

OQAQ (3)

28 Was bias in the selection avoided

OQAQ (4)

.81

29 Were the criteria used for assessing the validity reported?

OQAQ (5)

.75

30 Was the validity of all studies referred to in the text assessed using appropriate criteria

OQAQ (6)

.53

.60

31 Were the methods used to combine the finding of the relevant studies reported

OQAQ (7)

32 Were the findings of the relevant studies combined appropriately

OQAQ (8)

.78

33 Were the conclusions made by the author supported by the data

OQAQ (9)

.68

34 Overall Summary

OQAQ (10)

35. Publication Bias 2

Additional (1)

.80

36 Publication Status

Additional (2)

.77

37 Language 2

Additional (3)

.63

Shea et al. BMC Medical Research Methodology 2007 7:10 doi:10.1186/1471-2288-7-10