Diagnostic approach to the patient with a suspected inherited platelet disorder: Who and how to test.

Bleeding and thrombocytopenia are common referrals to the pediatric and adult hematology practice. The differential diagnosis encompasses a wide spectrum of entities that vary in acuity, severity, and etiology. Most will be acquired (especially in adult patients), but many can be inherited, and some may have manifestations affecting other organ systems. The first step: defining whether the symptoms and/or laboratory findings are clinically significant and warrant additional work-up, can be equally as challenging as reaching the diagnosis itself. How much bleeding is too much to be considered normal? How low of a platelet count is too low? Once the decision has been made to pursue additional studies, considering the increasing number of laboratory tests available, the diagnostic process can be complex. In this article, we outline a general approach for the evaluation of patients in whom an inherited platelet disorder is being considered. We present two clinical vignettes as introduction to the diagnostic approach to inherited platelet disorders. We describe the rationale for the different types of tests that are clinically available, their limitations, and finally the challenges that are frequently encountered in the interpretation of results. We also intend to provide some guidance on the expected phenotype in terms of severity of bleeding and/or thrombocytopenia according to the etiology of the inherited disorder. Our goal is to provide the practicing hematologist with a practical framework that is clinically applicable in their daily practice.