| Study | Randomisation/allocation concealment appropriate | Blinding* | Sample size calculation appropriate | ITT analysis appropriate | Dropouts (% of patients) ML/control | Quality domain |
| Montelukast+ICS vs ICS monotherapy | ||||||
| Laviolette 199918 | Yes/yes | Yes | Incomplete† | Unclear | 8/11 | 3 |
| Riccioni 200219 | Unclear/unclear | No | na | Yes | na | 3‡ |
| Vaquerizo 200320 | Yes/yes | Yes | Yes | Yes | 10/10 | 1 |
| Kanniess 200221 | Unclear/unclear | Yes | Incomplete† | Yes | 12/8 | 3‡ |
| Löfdahl 199922 | Yes/yes | Yes | Incomplete† | Yes | 16/27 | 1 |
| Riccioni 200523 | Unclear/unclear | Unclear | No | No | 9/13 | 3‡ |
| Tohda 200224 | Unclear/unclear | Yes | Yes | No | 6/7 | 3‡ |
| Montelukast+ICS vs salmeterol+ICS | ||||||
| Bjermer 200325 42 | Yes/yes | Yes | Yes | Yes | 17/15 | 1 |
| Grosclaude 200327 | Unclear/unclear | No | na | No | 13/6 | 3 |
| Ilowite 200428 43 | Yes/unclear | Yes | Yes | No | 17/16§ | 2 |
| Nelson 200029 44 45 | Yes/yes | Yes | Yes | Yes | 13/11 | 1 |
| Ringdal 200330 46 47 | Yes/unclear | Yes | Yes | No | 10/5 | 3¶ |
| SAM40030 200326 48 | Yes/yes | Yes | No** | Yes | 12/27 | 1** |
Definition of quality domain: 1 = no deficiencies (study meets all quality criteria), 2 = minor deficiencies (deficiencies do not affect the main conclusion), 3 = major deficiencies (deficiencies challenge the main conclusion).
*Blinding of patients, investigators and assessors of outcome measures; †no details for SD given in sample size calculation; ‡primary objective not defined; §85 patients in the ML/ICS group and 84 in the salmeterol/ICS group were excluded after randomisation because of over recruitment; ¶“major deficiencies” because of exclusion of patients who violated the study protocol; and **explorative study without sample size calculation and adjustment for multiple primary outcomes.
ICS, inhaled corticosteroids; ITT, intention to treat; ML, montelukast; na, not available.