| Trials | Randomisation methods | Double-blind | Follow-up | Intent to treat | Quality (score)a | Level of evidenceb |
| Andrew Tutt [14] | non-randomised | No | No patients was lost. | Yes | 1 | 1 |
| M. William Audeh [13] | non-randomised | No | No patients was lost. | Yes | 1 | 1 |
| Karen A. Gelmon [18] | non-randomised | No | No patients was lost. | 2 of 65 excluded from analysis | 1 | 4 |
| Stan B. Kaye [19] | Global Randomization system | No | NA | Yes | 4 | 1 |
| Jonathan Ledermann [12] [23] | NA | Yes | Rate of loss to follow-up 2.2% in olaparib group 3.9% in placebo group | Yes | 5 | 1 |
| Bella Kaufman [20] | non-randomised | No | NA | Yes | 0 | 4 |