By Dr. Salim Rezaie
Hematology is a subject that comes up daily in clinical practice, and is a favorite on the ABIM
Internal Medicine board exam. Evaluation of anemia, as well as some other hematologic
disorders, is paramount for an internist to master. I will try and provide five evidence-based
pearls in this post that will help physicians understand some important concepts and avoid
common pitfalls in the recognition and treatment of such hematological disorders.
Pearl #1: Patients on iron supplementation SHOULD NOT have positive guaiac tests.
Studies in vitro show ferric iron (Fe3+) will give a positive guaiac reaction and ferrous
iron (Fe2+) does not
Iron is digested in the ferrous form and carried in the blood in the ferric form
Patients on iron supplementation with positive guaiac require screening for identifying
the source of gastrointestinal hemorrhage
Ferrous (Fe2+) iron does not cause positive guaiac tests in vivo
Pearl #2: The pentad of Thrombotic Thrombocytopenic Purpura (TTP) is not always