Comparison 1. Prophylactic platelet transfusion at a standard trigger level versus a higher trigger level.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Numbers of participants with a significant bleeding event	3	499	Risk Ratio (M‐H, Fixed, 95% CI)	1.35 [0.95, 1.90]
1.1 Platelet threshold < 10 vs. < 20	2	333	Risk Ratio (M‐H, Fixed, 95% CI)	1.41 [0.95, 2.10]
1.2 Platelet threshold < 10 vs. < 30	1	166	Risk Ratio (M‐H, Fixed, 95% CI)	1.19 [0.59, 2.37]
2 Number of participants with WHO Grade 3 or 4 bleeding	2	421	Risk Ratio (M‐H, Fixed, 95% CI)	0.99 [0.52, 1.88]
2.1 Platelet threshold < 10 vs. < 20	1	255	Risk Ratio (M‐H, Fixed, 95% CI)	1.21 [0.58, 2.54]
2.2 Platelet threshold < 10 vs. < 30	1	166	Risk Ratio (M‐H, Fixed, 95% CI)	0.55 [0.14, 2.13]
3 Number of participants with bleeding requiring a red cell transfusion	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
4 Time to first bleeding episode	1		Hazard Ratio (Fixed, 95% CI)	Subtotals only
5 All‐cause mortality	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
6 Mortality due to bleeding	3		Risk Ratio (M‐H, Fixed, 95% CI)	Totals not selected
7 Mortality due to bleeding (all randomised participants)	3		Odds Ratio (M‐H, Fixed, 95% CI)	Totals not selected
8 Mortality due to infection	1		Odds Ratio (M‐H, Fixed, 95% CI)	Subtotals only
9 Mean number of platelet transfusions per participant	2	333	Mean Difference (IV, Fixed, 95% CI)	‐2.09 [‐3.20, ‐0.99]
10 Mean number of red cell transfusions per participant	2	333	Mean Difference (IV, Fixed, 95% CI)	0.66 [‐0.43, 1.76]
11 Complete remission rates	2	333	Risk Ratio (M‐H, Fixed, 95% CI)	0.92 [0.78, 1.09]
12 Numbers of participants with platelet transfusion reactions	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
13 Number of participants with thromboembolic disease	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
14 Number of participants requiring HLA‐matched platelets	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
15 Number of participants with platelet refractoriness	2	244	Risk Ratio (M‐H, Fixed, 95% CI)	0.66 [0.16, 2.67]
16 Numbers of participants with a significant bleeding event	3	499	Risk Ratio (M‐H, Fixed, 95% CI)	1.35 [0.95, 1.90]
16.1 Platelet component dose (2.9 x 1011 to 4.9 x 1011)	2	244	Risk Ratio (M‐H, Fixed, 95% CI)	1.71 [1.04, 2.82]
16.2 Platelet component dose (< 2.9 x 1011)	1	255	Risk Ratio (M‐H, Fixed, 95% CI)	1.07 [0.66, 1.74]