23. Overview of results: Orthopaedic (spinal).

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 0.44 [0.31, 0.63] 3 RCTs, N = 194 ⨁⨁⨁◯	RR 0.43 [0.26, 0.71] 2 RCTs, N = 144 ⨁⨁⨁◯	RR 0.50 [0.05, 5.17] 1 RCT, N = 50 ⨁◯◯◯		RR 0.32 [0.18, 0.58] 1 RCT, N = 49 ⨁⨁◯◯	RR 0.50 [0.05, 5.17] 1 RCT, N = 50 ⨁◯◯◯	RR 0.54 [0.34, 0.86] 1 RCT, N = 95 ⨁⨁⨁◯
Volume transfused (PPR)	MD ‐0.99 [‐2.49, 0.50] 3 RCTs, N = 208 ⨁◯◯◯	MD ‐1.39 [‐3.48, 0.71] 2 RCTs, N = 145 ⨁◯◯◯	MD ‐0.21 [‐0.63, 0.21] 1 RCT, N = 63 ⨁⨁◯◯				MD ‐0.99 [‐2.49, 0.50] 3 RCTs, N = 208 ⨁◯◯◯
Volume transfused (PPT)	MD 0.59 [‐0.09, 1.27] 1 RCT, N = 45 ⨁◯◯◯	MD 0.59 [‐0.09, 1.27] 1 RCT, N = 45 ⨁◯◯◯					MD 0.59 [‐0.09, 1.27] 1 RCT, N = 45 ⨁◯◯◯
All‐cause mortality
Blood loss	MD ‐121.37 [‐245.90, 3.15] 3 RCTs, N = 208 ⨁⨁⨁◯	MD ‐111.92 [‐238.45, 14.60] 2 RCTs, N = 145 ⨁⨁⨁◯	MD ‐413.00 [‐1115.93, 289.93] 1 RCT, N = 63 ⨁⨁⨁◯				MD ‐121.37 [‐245.90, 3.15] 3 RCTs, N = 208 ⨁⨁⨁◯
Re‐operation
Infection	RD 0.00 [‐0.06, 0.06] 1 RCT, N = 63 ⨁⨁◯◯		RD 0.00 [‐0.06, 0.06] 1 RCT, N = 63 ⨁⨁◯◯				RD 0.00 [‐0.06, 0.06] 1 RCT, N = 63 ⨁⨁◯◯
Wound complication	RR 4.44 [0.22, 88.04] 1 RCT, N = 49 ⨁◯◯◯	RR 4.44 [0.22, 88.04] 1 RCT, N = 49 ⨁◯◯◯			RR 4.44 [0.22, 88.04] 1 RCT, N = 49 ⨁◯◯◯
PJI
VTE/thrombosis
DVT
PE	POR 8.17 [0.16, 413.39] 1 RCT, N = 63 ⨁◯◯◯		POR 8.17 [0.16, 413.39] 1 RCT, N = 63 ⨁◯◯◯				POR 8.17 [0.16, 413.39] 1 RCT, N = 63 ⨁◯◯◯
MACE
MI
CVA/stroke
Hospital LOS

Bolded data highlights where there was a clear intervention 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