Original Article

Elevated Red Cell Distribution Width in the Diagnosis of Thrombotic Thrombocytopenic Purpura in Patients Presenting with Anemia and Thrombocytopenia

Authors: Nagaprasad Nagajothi, MD, Albert Braverman, MD


Objective: To determine if red cell distribution width (RDW) is elevated in thrombotic thrombocytopenic purpura (TTP) and to evaluate the sensitivity and specificity of such elevation in the diagnosis of TTP.

Methods: We retrospectively studied red cell distribution width at presentation in 25 consecutive patients with newly diagnosed TTP who were treated with plasmapheresis in our institution between 1997 to 2005. Control patients consisted of 20 consecutive patients without TTP who presented to the emergency room (ER) with anemia and thrombocytopenia.

Results: Patients with TTP had significantly elevated RDW compared with the controls (23.1% versus 17.2% respectively, P = 0.0001). An RDW >18% had a 95% sensitivity and 70% specificity in the diagnosis of TTP, whereas RDW >19% had 80% sensitivity and 85% specificity.

Conclusions: TTP should be suspected in patients presenting with unexplained anemia and thrombocytopenia with an RDW ≥18%.

Key Points

* Red cell distribution width (RDW) is frequently elevated in thrombotic thrombocytopenic purpura (TTP).

* Suspect TTP in patients presenting with unexplained anemia and thrombocytopenia with elevated RDW.

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1. Allford SL, Hunt BJ, Rose P, et al. Guidelines on the diagnosis and management of the thrombotic microangiopathic hemolytic anemias. Br J Haematol 2003;120:556–573.
2. Furlan M, Robles R, Galbusera M, et al. Von Willebrand factor-cleaving protease in thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome. N Engl J Med 1998;339:1578–1584.
3. Tsai HM, Lian EC. Antibodies to von Willebrand factor-cleaving protease in acute thrombotic thrombocytopenic purpura. N Engl J Med 1998;339:1585–1594.
4. George JN. How I treat patients with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome. Blood 2000;96:1223–1229.
5. Moake JL. Thrombotic microangiopathies. N Engl J Med 2002;347:589–600.
6. Roberts GT, El Badawi SB. Red blood cell distribution width index in some hematologic diseases. Am J Clin Pathol 1985;83:222–226.
7. Saxena S, Weiner JM, Carmel R, et al. Red blood cell distribution width in untreated pernicious anemia. Am J Clin Pathol 1988;89:660–663.
8. Qrtom HA, al-Saleh QA, Lubani MM, et al. The value of red cell distribution width in the diagnosis of anemia in children. Eur J Pediatr 1989;148:745–748.
9. Schweiger DJ. Red cell distribution width in sickle cell anemia. Am J Med Technol 1981;47:231–233.
10. Aslan D, Gumruk F, Gurgey A, et al. Importance of RDW value in differential diagnosis of hypochromic anemias. Am J Hematol 2002;69:31–33.
11. Banno S, Ito Y, Tanaka C, et al. Quantification of red blood cell fragmentation by the automated hematology analyzer XE-2100 in patients with living donor liver transplantation. Clin Lab Haematol2005;27:292–296.