Approach to suspected drug-induced immune thrombocytopenia (DITP)

DIC: disseminated intravascular coagulation; HIT: heparin-induced thrombocytopenia; ICU: intensive care unit; ITP: immune thrombocytopenia; IVIG: intravenous immune globulin.

* One or more drugs may be held or stopped (unless the risk of stopping is too high). The choice of which drug(s) to stop is based on:

• Timing of when they were started related to onset of thrombocytopenia
• Likelihood of causing thrombocytopenia for each drug
• Results of testing for other causes of thrombocytopenia such as infection and disseminated intravascular coagulation (DIC)

Drug-dependent antibody testing and future drug avoidance can be pursued if the clinical presentation clearly evolves to favor DITP as the likely diagnosis, based on lack of other diagnoses and resolution of thrombocytopenia on drug discontinuation.

¶ One exception is heparin-induced thrombocytopenia (HIT), in which the timing of platelet count drop is 5 to 10 days after heparin exposure (if initial heparin exposure is within the past 5 to 30 days) or within 1 day of reexposure (if exposed to heparin in the previous 31 to 100 days). In HIT, the nadir platelet count is approximately 60,000/microL, and platelet counts <20,000/microL are rare. HIT and other exceptions to the timing of platelet count drop are discussed in UpToDate.