Woodfine 2011.

Methods	A randomised controlled trial.   Recruitment period not stated. Follow‐up 4 months and 12 months from randomisation (approx 3 and 11 months from intervention). Collaborating partners Lead agency: Public health Commissioning and strategic involvement: CHARISMA Study Group(Children’s Health in Asthma Research to Improve Status by Modifying Accommodation) ‐ Wrexham County Borough Council, Wrexham public health team (National Public Health Service Wales), Betsi Cadwalydr University Health Board  and academia Operational: GPs identified families, Wrexham County Borough Council paid for and provided housing modifications. Family surveys  and installation undertaken by Housing Officers. Set in UK
Participants	192 children aged 5‐14 years living in Wrexham, UK, registered with one of 20 participating GP practices, who had received ≥3 prescriptions of corticosteroid inhalers in the preceding year and with written consent from parent/guardian to take part, complete questionnaires, and allow access to child’s medical records. Children with Cystic Fibrosis, or who were likely to move away within 12 months or whose home had a ventilation system already installed and adequate central heating at pre‐randomisation base line were all excluded. Elibigle: 445; recruited 195 (includes 3 siblings); 192 randomised: I = 96; C = 96.
Interventions	Installation of Vent‐Axia HR200XL ventilation system in the roof space and improvement/replacement of central heating system if required; all delivered by local government. Note: trial protocol indicates single room ventilation system if a single child but study report indicates that installation was in the roof space. Control: Nothing. Wait list (12 months)
Outcomes	Month 4 (3 months post intervention):  173 [90%] I = 87; C = 86 Month 12 (11 months post intervention): 169 [88%] I = 88; C = 89. Parent‐completed asthma‐specific, physical and psychosocial subscores of PedsQL (a validated quality of life measure for children), Childrens' mean days off School over the study period for all causes and for asthma. Cost effectiveness of intervention measured. Shift from ‘severe’ to ‘moderate’ asthma: I = 17% ; C =3% Mean cost of modifications: £1718 per child treated or £12,300 per child shifted from ‘severe’ to ‘moderate’. No significant difference in healthcare costs over 12 months between groups.  ‘Bootstrapping’ gave an incremental cost‐effectiveness ratio (ICER) of £234 per point improvement on the 100‐point PedsQL™ asthma‐specific scale (95% CI: £140 to £590). ICER fell to £165 (95%CI: £84 to £424) for children with ‘severe’ asthma.
Notes	Study underpowered: power calculation required 200 children to detect a change in asthma‐specific QoL of ≥0.4 of asthma‐specific PedsQL. Study is a ventilation enhancement intervention and was not designed to explore the effect of local government and local health collaboration versus separate services. Thus it’s unclear how much the study can contribute to answering the review question. Significant additional resource required (see cost‐effectiveness data above). Treatment fidelity: Yes, other than installing ventilation in roof space rather than for single room as stated in protocol. Overall risk of bias: Low
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Low risk	Remote allocation concealment using contemporaneous dynamic randomisation.
Blinding (performance bias and detection bias) All outcomes	Low risk	Blinded outcome assessment, although not possible to blind participants
Incomplete outcome data (attrition bias) All outcomes	Low risk	≥88% at each time point
Selective reporting (reporting bias)	Low risk	Unselective reporting – as per registered protocol: ISRCTN13912429
Other bias	Low risk	Randomisation and control children paired to avoid seasonal bias
Randomisation adequately described/protected?	Low risk	Stratified randomisation well described.
Protection against contamination?	Low risk	Unlikely control families would have installed ventilation.
Follow‐up rate adequate?	Low risk	Outcome data available for 88% at 12 months and balanced in both arms.
Reliable primary outcome measure?	Unclear risk	Subjective data but validated tool (PedsQL)
Groups measured at baseline?	Low risk	Groups stratified. Significant difference between groups for social functioning.
Appropriate choice of controls (CBA studies only)?	Unclear risk	Not applicable
Contemporaneous data collection (CBA studies only)?	Unclear risk	Not applicable
IS THE STUDY AT LOW RISK OF BIAS?	Low risk	OVERALL RISK OF BIAS WAS LOW