Table 2.
Summary of results for reporting and analysing for confounding
| Main analysis | DS1 | DS2 | |
| N | 211 | 131 | 115 |
| Adjusted and crude analysis presented | 181 (86%) | 112 (85%) | 100 (87%) |
| Crude analysis presented only | 22 (10%) | 12 (9%) | 9 (8%) |
| Adjusted analysis presented only | 8 (4%) | 8 (6%) | 6 (5%) |
| Method of selection for adjustment covariates* | |||
| A priori/wisely | 114 (54%) | 77 (59%) | 69 (60%) |
| Stepwise method | 37 (17%) | 19 (15%) | 15 (13%) |
| Bivariate selection | 45 (21%) | 25 (19%) | 21 (18%) |
| Unknown | 20 (9%) | 12 (9%) | 11 (10%) |
| Other | 1 (0%) | 1 (1%) | 1 (1%) |
| Method of adjustment for confounding* | |||
| Multivariable model | 146 (69%) | 88 (67%) | 88 (77%) |
| Stratification | 9 (4%) | 5 (4%) | 5 (4%) |
| Matching | 17 (8%) | 14 (11%) | 14 (12%) |
| Inverse probability weighting | 7 (3%) | 5 (4%) | 5 (4%) |
| Propensity score | 26 (12%) | 23 (18%) | 23 (20%) |
| Restriction | 0 | 0 | 0 |
| Other | 1 (0%) | 0 | 0 |
DS1: Dataset 1 includes only studies where the comparison of at least two treatments was the main exposure of interest (head to head studies).
DS2: Dataset 2 includes only studies from DS1, which had no other outcome than effectiveness.
*Sum of the methods may be greater than the numbers of studies as some studies used several methods.