Patient treatments are stratified by the presence or absence of bleeding and in the non bleeding patient by the platelet number and the presumed cause of the<unk> 
most if not all of the following thresholds are based on weak recommendations with low quality evidence
<50K if planned lumbar puncture or neurosurgical procedure
<20K if planned for central venous catheter placement (preference toward compressible site), or febrile patient
<10K in asymptomatic patients (unless due to ITP, TTP, or HIT)
There are no firm recommendations for transfusion thresholds in acute traumatic bleeding but many providers will opt for a goal of 100K, especially if there is evidence of ICH
TTP, DIC, HIT
1 unit of platelets per 5kg body weight raises count by 50k
Thrombocytopenia
Marrow infiltration 
Thrombocytosis
Viral infections 
Neutropenia
Marrow suppression 
Leukopenia
Congenital thrombocytopenia