Using decision analysis techniques to deal with "unanswerable" questions in idiopathic thrombocytopenic purpura.

Idiopathic thrombocytopenic purpura (ITP) is a common disorder with rare adverse outcomes. This makes it a particularly difficult area in which to undertake conventional studies. An alternative method for solving clinical questions is decision analysis, which is in essence a computer-assisted synthesis of the literature. Using the example of a newly diagnosed ITP patient, the author attempts to answer the question of whether a bone marrow aspirate (BMA) is required prior to starting steroids. Using decision analysis methodology, the author determines that BMA is not essential prior to starting steroids. More importantly, three variables critical to the decision-making process are determined: the risk of death from the BMA procedure, the altered chance of survival for a patient with acute lymphoblastic leukemia (ALL) inappropriately given steroids, and how sensitive the complete blood count is at determining the risk of ALL. This scenario demonstrates the value of decision analysis and lays the groundwork for future endeavors.