Comparison 1. PAD versus control (Blood Transfused).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 No. Exposed to Allogeneic Blood Transfusion	13	1506	Risk Ratio (M‐H, Random, 95% CI)	0.32 [0.22, 0.47]
2 No. Exposed to Allogeneic Blood Transfusion (Operation Type)	13	1506	Risk Ratio (M‐H, Random, 95% CI)	0.32 [0.22, 0.47]
2.1 Orthopaedic	5	425	Risk Ratio (M‐H, Random, 95% CI)	0.21 [0.11, 0.43]
2.2 Oncology	6	985	Risk Ratio (M‐H, Random, 95% CI)	0.48 [0.35, 0.66]
2.3 Oral and maxillofacial	1	48	Risk Ratio (M‐H, Random, 95% CI)	0.02 [0.00, 0.28]
2.4 Cardiac	1	48	Risk Ratio (M‐H, Random, 95% CI)	0.06 [0.00, 1.02]
3 No. Exposed to Allogeneic Blood Transfusion (Transfusion Protocol)	13	1506	Risk Ratio (M‐H, Random, 95% CI)	0.32 [0.22, 0.47]
3.1 Transfusion Protocol	9	1289	Risk Ratio (M‐H, Random, 95% CI)	0.45 [0.34, 0.61]
3.2 No Transfusion Protocol	4	217	Risk Ratio (M‐H, Random, 95% CI)	0.12 [0.04, 0.33]
4 No. Exposed to Allogeneic / Autologous Blood Transfusion	11	1315	Risk Ratio (M‐H, Random, 95% CI)	1.24 [1.02, 1.51]
5 No. Exposed to Allogeneic / Autologous Blood Transfusion (Operation Type)	11	1315	Risk Ratio (M‐H, Random, 95% CI)	1.24 [1.02, 1.51]
5.1 Orthopaedic	3	234	Risk Ratio (M‐H, Random, 95% CI)	1.78 [0.61, 5.20]
5.2 Oncology	6	985	Risk Ratio (M‐H, Random, 95% CI)	1.33 [1.15, 1.54]
5.3 Oral and maxillofacial	1	48	Risk Ratio (M‐H, Random, 95% CI)	1.0 [0.92, 1.09]
5.4 Cardiac	1	48	Risk Ratio (M‐H, Random, 95% CI)	0.79 [0.31, 2.00]
6 No. Exposed to Allogeneic / Autologous Blood Transfusion (Transfusion Protocol)	11	1315	Risk Ratio (M‐H, Random, 95% CI)	1.24 [1.02, 1.51]
6.1 Transfusion Protocol	7	1098	Risk Ratio (M‐H, Random, 95% CI)	1.34 [1.08, 1.68]
6.2 No Transfusion Protocol	4	217	Risk Ratio (M‐H, Random, 95% CI)	1.07 [0.93, 1.23]
7 Pre‐operative haemoglobin levels (g/dL)	6	582	Mean Difference (IV, Random, 95% CI)	‐1.09 [‐1.50, ‐0.68]