Key Takeaways

When faced with a patient with thrombocytopenia, consider possible underlying mechanisms (pseudothrombocytopenia, decreased production, increased destruction and splenic sequestration) and more importantly the clinical context (outpatient, urgent care/emergency department, non-intensive care unit (ICU) medical inpatient, non-ICU surgical inpatient, ICU and obstetrics). The pretest probability of one or another cause of thrombocytopenia varies immensely according to the clinical context.

Immune thrombocytopenia (ITP) is a diagnosis of exclusion.

ITP may occur as a primary disorder or secondary to a predisposing illness.

If you suspect ITP (for example, there are no other obvious cause of thrombocytopenia in an outpatient), test for HIV and HCV serology because treatment of the underlying viral infection may improve platelet counts.

There is no need to do a bone marrow biopsy if the patient is presenting with typical ITP, that is the hemoglobin and white cell count are normal and the peripheral smear is unremarkable except for a paucity of platelets.

First-line therapy for newly diagnosed ITP consists of steroids, either prednisone which should be tapered off over the next 6-8 weeks, or dexamethasone, which is given at high dose over 4 days, repeated up to three times.