Avenell 2004.

Methods	Randomised clinical trial using 2 x 2 factorial design.
Participants	Country: United Kingdom. Number of participants randomised: 134, aged 70 years or over (mean age 77), 83% women. Inclusion criteria: people aged 70 years or over with an osteoporotic fracture within the last 10 years. Exclusion criteria: daily oral treatment with more than 200 IU (5 µg) vitamin D or more than 500 mg calcium or other bone active medications.
Interventions	Participants were randomly assigned to receive: Intervention group 1: vitamin D3 (800 IU) daily (n = 35); Intervention group 2: calcium (1000 mg) daily (n = 29); Intervention group 3: vitamin D3 (800 IU) plus calcium (1000 mg) daily (n = 35); Intervention group 4 (Control group): no tablets daily (n = 35); for a one‐year period. The calcium supplements were provided as calcium carbonate.
Outcomes	Primary outcomes were recruitment, compliance, and retention within a randomised trial.
Stated aim of study	"To assess the effects of an open trial design (without placebo and participants knowing what tablets they were given) when compared with a blinded, placebo‐controlled design on recruitment, compliance, and retention within a randomised trial of secondary osteoporotic fracture prevention."
Notes	"All participants were asked to return unconsumed tablets for a tablet count compliance. Compliance amongst those who returned their tablet containers was similar (overall 85% versus 84.5% of tablet takers took their tablets on more than 80% of days). The same pattern was observed for self‐reported tablet consumption at four, eight or 12 months during the trial." "Shire Pharmaceuticals funded the capsules, which were co‐funded and manufactured by Nycomed." Additional information on mortality was received through personal communication with Dr Alison Avenell (28.01.2009).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Sequence generation was achieved using computer random number generation.
Allocation concealment (selection bias)	High risk	Participants were told to which compound they had been allocated.
Blinding (performance bias and detection bias) All outcomes	High risk	Trial was not blinded, so that the allocation was known during the trial. Participants were told to which compound they had been allocated. Placebo was not used.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The numbers and reasons for dropouts and withdrawals in all intervention groups were described.
Selective reporting (reporting bias)	Low risk	Pre‐defined, or clinically relevant and reasonably expected outcomes are reported on.
Industry bias	Unclear risk	"Shire Pharmaceuticals funded the capsules, which were co‐funded and manufactured by Nycomed."
Other bias	Low risk	The trial appears to be free of other components that could put it at risk of bias.