1. Characteristics of the included studies.

Study	Type of participants	Number of participants	Intervention	Platelet component dose	Duration of study	Type of platelet component	Primary outcome
Diedrich 2005	All ages undergoing an allogeneic HSCT	166	Prophylactic plt transfusion if plt count < 10 x 109/L versus prophylactic plt transfusion if plt count < 30 x 109/L	Average yield (mean ± SD) 4.10 x 1011 ± 0.2 x 1011 (buffy coat) 3.80 x 1011 ± 0.2 x 1011 (apheresis)	Maximum duration of observation was 37 days (7 days pre‐HSCT and 30 days post‐HSCT). No information available on the number of participants who died or were lost to follow‐up	Leucodepleted, ABO ‐matched, irradiated pooled random‐donor platelets (buffy coat) 85% Apheresis 15%	Number of platelet transfusions
Heckman 1997	Adults with acute leukaemia	82	Prophylactic plt transfusion if plt count ≤ 10 x 109/L versus prophylactic plt transfusion if plt count ≤ 20 x 109/L	1 apheresis unit. Average yield each study year (number of transfusions) 4.9 x 1011 1991 (n = 502) 4.5 x1011 1992 (n = 418) 4.7 x 1011 1993 (n = 399) 4.0 x 1011 1994 (n = 400) 4.3 x 1011 1995 (n = 398)	Median 24 days	Leucodepleted Apheresis	Not reported
Rebulla 1997	Adolescents and adults with AML	276	Prophylactic plt transfusion if plt count < 10 x 109/L versus prophylactic plt transfusion if plt count < 20 x 109/L	Median 2.2 x 1011 (pooled) 2.8 x 1011 (apheresis)	Mean 27.8 to 29.7 days	Apheresis and pooled products	Frequency and severity of haemorrhage

AML = acute myeloid leukaemia

HSCT = haematopoietic stem cell transplant

plt = platelet

SD = standard deviation