Jolley 2004.

Methods	RCT with unclear follow‐up period, mean bed days observed/participant Group 1: 7 days, and Group 2: 7.9 days.
Participants	Participants recruited from a single hospital, and had to be at low to moderate risk of developing a pressure ulcer and > 18 y. Patients were excluded if they had no risk or high risk (as more complex interventions required), if they had any pre‐existing ulcers, had an expected length of stay of < 48 h or had darkly‐pigmented skin (justified by authors as making grade 1 ulcers difficult to detect). Participants well matched at baseline for age, sex, mean pressure ulcer risk score.
Interventions	1. Sheepskin mattress overlay: leather‐backed with a dense, uniform 25 mm wool pile.  Used as a partial mattress overlay.  Pressure points that were not covered by sheepskin were protected by a second sheepskin, or specific sheepskin elbow and heel protectors. Overlays were changed 3 times a week (unless required). Received usual care including repositioning (n = 270). 2. Usual care as determined by ward staff. Included repositioning and any other PRD or prevention strategy with/without low‐tech constant pressure relieving devices (n = 269).
Outcomes	Number of participants with incidence pressure ulcer (daily assessment; unblinded outcome assessment): All ulcers (grade 1 and 2; no grade 3 or 4 recorded) 1. Sheepskin: 10% (21/218); 2. Usual care: 17% (37/223). Total number of ulcers: 1. Sheepskin: 27; 2. Usual care: 58. Total number of incident grade 2 ulcers: 1. Sheepskin: 12; 2. Usual care: 20.
Notes	Whilst 270 were allocated to the sheepskin and 269 to control; only 218 and 223 received their allocated treatment and are included in the analysis. Not ITT. "Any patient whose risk increased to high (Braden score <12) for 48 h was no longer followed up for pressure‐ulcer endpoints."  Authors did not say why. Of the 218 participants in the sheepskin group 2 died, 7 became high risk (treatment change), 14 requested withdrawal, 6 had ward staff intervention and 11 changed treatment for other reasons. Of the 223 control participants 5 died, 1 became high risk, 8 requested withdrawal, 5 had ward staff intervention and 10 changed treatments for other reasons.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Shuffling cards(?): "Patients were randomly allocated to receive.......using numbered cards in individually sealed opaque envelopes; blocks of 16 envelopes (eight of each group) were shuffled before use".
Allocation concealment (selection bias)	Low risk	"Patients were randomly allocated to receive.......using numbered cards in individually sealed opaque envelopes; blocks of 16 envelopes (eight of each group) were shuffled before use".
Blinding (performance bias and detection bias) Pressure ulcer incidence	High risk	"As it was logistically impossible to blind patients, ward staff and research nurses to the treatment group this was an open‐label, unblinded trial".
Incomplete outcome data (attrition bias) All outcomes	High risk	"539....were randomly allocated. Of these, 441 received the allocated intervention. All 441 were followed up to the endpoints...".  Data for 441 not 539. Is a per protocol analysis.
Selective reporting (reporting bias)	Low risk	All pre‐specified outcomes reported.
Free of other bias ‐ were groups similar at baseline regarding the most important prognostic indicators?	Unclear risk	Baseline data for 441 participants and not the 539 randomised.
Free of other bias ‐ was the timing of the outcome assessment similar in all groups?	Low risk	"Research nurse assessed each participant daily for pressure ulcer risk.....and skin integrity".