Kraus 2002.

Methods	RCT
Participants	Subjects: 12772 home attendants, 12408 female and 364 male. No more information about inclusion and exclusion criteria.
Interventions	Preventive intervention: 1) lumbar support (n=3837), 28 months. Control interventions: 2) 1 safety meeting with information about low back health (n=4300) 3) no intervention (n=4635)
Outcomes	Back injury rates. The lumbar support group had less back injuries than the information group (not significant) and no intervention group (significant).
Notes	A cluster‐randomised trial design was chosen: 9 agencies were chosen a priori and randomised. Few data available regarding baseline and differences between groups. Compliance per month: 80 ‐ 97%.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	High risk
Allocation concealment?	Unclear risk	B ‐ Unclear
Blinding? All outcomes ‐ patients?	High risk
Blinding? All outcomes ‐ outcome assessor?	Low risk
Incomplete outcome data addressed? All outcomes ‐ drop‐outs?	High risk
Incomplete outcome data addressed? All outcomes ‐ ITT analysis?	High risk
Similarity of baseline characteristics?	Unclear risk	Few data available regarding baseline and differences between groups.
Co‐interventions avoided or similar?	High risk
Compliance acceptable?	Low risk	Compliance per month: 80 ‐ 97%.
Timing outcome assessments similar?	Low risk