Table 2.
More advanced applications of l2 for assessing heterogeneity in three published meta-analyses. Meta-analyses were conducted with either meta or metan in STATA15
|
Heterogeneity test
|
|||||||
|---|---|---|---|---|---|---|---|
| Topic | Outcome/analysis | Effect measure | No of studies | Q | df | P | I2 (95% uncertainty intervals)* |
| Magnetic fields and leukaemia19 | All studies
|
Odds ratio
|
6
|
15.9
|
5
|
0.007
|
69 (26 to 87)
|
| High quality
|
Odds ratio
|
3
|
2.4
|
2
|
0.31
|
17 (0 to 91)
|
|
| Low quality | Odds ratio | 3 | 9.4 | 2 | 0.009 | 79 (32 to 94) | |
| Human albumin for critically ill20 | Death
|
Risk ratio
|
24†
|
15.3
|
23
|
0.88
|
0 (0 to 17)
|
| Death | Risk difference | 30 | 36.7 | 29 | 0.15 | 21 (0 to 50) | |
| Tamoxifen to prevent recurrence of breast cancer17 | All studies
|
Peto odds ratio
|
55
|
108.2
|
54
|
0.00002
|
50 (32 to 63)
|
| Total within groups‡
|
Peto odds ratio
|
—
|
59.9
|
52
|
0.21
|
13 (0 to 39)
|
|
| Between groups‡ | Peto odds ratio | 3 groups | 48.3 | 2 | <0.00001 | 96 (91 to 98) | |
df=degrees of freedom,
*
Values of l2 are percentages. 95% uncertainty intervals are calculated as proposed by Higgins and Thompson.14
†
Studies with no events in either treatment group do not contribute to this analysis.
‡
Subgroup defined by duration of tamoxifen treatment.