Åhman 2000.
| Methods | Controlled before‐after study | |
| Participants | Pupils and personnel at 2 schools in Sweden 337 pupils and 34 personnel in the intervention school and 224 and 21 personnel in the control school | |
| Interventions | A new ventilated floor was installed and water damaged wallboards were exchanged | |
| Outcomes | Participants: physical and psycho‐social school environment parameters Frequency of irritating symptoms including respiratory symptoms |
|
| Notes | — | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Not blinded |
| Blinding of outcome assessment (detection bias) All outcomes | High risk | Not blinded |
| Unplanned subgroup analyses (16) | Low risk | No unplanned subgroup analyses |
| Follow‐up (17) | Unclear risk | Follow‐up time 7 months |
| Compliance (19) | Low risk | Compliance was reliable |
| Valid outcome measures (20) | Unclear risk | Subjective symptoms |
| Selection bias (population) (21) | Low risk | "These two schools (intervention school and the control school) were the only compulsory schools in this suburb, which had an even distribution of social factors, such as gender, immigrants and type of dwellings." |
| Selection bias (time) (22) | Low risk | The intervention and control group were interviewed at the same time |
| Random sequence generation (selection bias) | High risk | Not randomised |
| Allocation concealment (selection bias) | High risk | Not concealed |
| Adjustment for confounding (25) | Low risk | Distribution of known confounders in the intervention and control group was described |
| Incomplete outcome data (26) (attrition bias) | Low risk | Results were presented only for those who participated in both pre‐ and post‐intervention interviews |
cRCT = cluster‐randomised controlled trial HVAC = heating ventilation and air‐conditioning RCT = randomised controlled trial SF‐36 = short‐form health survey