15. Overview of results: aggregate (all surgeries): primary outcome only.

Outcome	Total [95% CI]	Subgroup: blood salvage (collection time)			Subgroup: transfusion threshold
		Intraoperative	Postoperative	Both	No transfusion threshold	Liberal threshold (Hb > 80 g/L)	Restrictive threshold (Hb < / = 80 g/L)
Risk of transfusion	RR 0.66 [0.59, 0.72] 82 RCTs, N = 12520 ⨁◯◯◯	RR 0.70 [0.60, 0.82] 20 RCTs, N = 3193 ⨁⨁◯◯	RR 0.58 [0.50, 0.68] 52 RCTs, N = 5710 ⨁◯◯◯	RR 0.84 [0.71, 1.00] * 13 RCTs, N = 3617 ⨁⨁◯◯	RR 0.64 [0.49, 0.83] 20 RCTs, N = 3092 ⨁◯◯◯	RR 0.59 [0.50, 0.69] 35 RCTs, N = 3461 ⨁◯◯◯	RR 0.72 [0.61, 0.85] 27 RCTs, N = 5967 ⨁⨁◯◯

Three studies reported data for more than one collection period, and so appear in more than one subgroup for timing: Blatsoukas 2010 (Orthopaedic (knee): postoperative only and both); Parrot 1991 (Cardiovascular (with bypass): intraoperative only and both); Rollo 1995 (Orthopaedic (hip): postoperative only and both).

Bolded data highlights where there was a clear intervention effect.

* neared an intervention effect (touched the line of no effect)

"Volume" refers to mean transfusion volume; "transfusions" refers to number of people receiving an allogeneic transfusion

CI: confidence interval; CVA: cerebrovascular accident; DVT: deep vein thrombosis; Hb: haemoglobin; LOS: hospital length of stay; MACE: major adverse cardiovascular events; MD: mean difference; MI: myocardial infarction; N: number of people analysed; PE: pulmonary embolism; PJI: prosthetic joint infection; POR: Peto odds ratio; PPR: per person randomised; PPT: per person transfused; RCT: randomised controlled trial; RD: risk difference; RR: risk ratio; VTE: venous thromboembolism

⨁◯◯◯ = Very low certainty; ⨁⨁◯◯ = Low certainty; ⨁⨁⨁◯ = Moderate certainty; ⨁⨁⨁⨁ = High certainty