There is no evidence from RCTs to determine whether platelet transfusions are required prior to central line insertion in patients with thrombocytopenia, and, if a platelet transfusion is required, what is the correct platelet transfusion threshold. Further randomised trials with robust methodology are required to develop the optimal transfusion strategy for such patients. The one ongoing RCT involving people with cirrhosis will not be able to answer this review's questions, because it is a small study that assesses one patient group and does not address all of the comparisons included in this review. To detect an increase in the proportion of participants who had major bleeding from 1 in 100 to 2 in 100 would require a study containing at least 4634 participants (80% power, 5% significance).