The clinical diagnosis of thrombotic thrombocytopenia purpura (TTP) is a difficult one to make. It is based on clinical criteria, one of which is a microangiopathic hemolytic anemia, characterized morphologically by the presence of schistocytes on the peripheral blood smear. The ADVIA 2120 automated hematology analyzer is able to quantify the presence of red blood cell (RBC) fragments. We studied the ability of the ADVIA 2120 to be able to detect RBC fragments in the blood of TTP patients, and the characteristics of all patients in whom RBC fragments were obtained. During the study period, 6 TTP patients were studied. The initial numbers of RBC fragments ranged from 0.02–0.05 × 106 cells/μl. During the course of plasmapheresis, these numbers decreased to 0.00–0.02 × 106 cells/μl, corresponding to a rise in the platelet count.

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In the course of a month, 52 blood samples on 39 patients were flagged by the hematology analyzer to have RBC fragments (0.01–0.12 × 106 cells/μl).

52 Samples with RBC Fragment Flag

HemoglobinPlateletsRDW
Range 4– 14.3 g/dl 5–906 × 103/ul 13.9– 28.6% 
Number Abnormal 46 (<13.0 g/dl) 23 (<160 × 103/ul) 51 (>14.1%) 
HemoglobinPlateletsRDW
Range 4– 14.3 g/dl 5–906 × 103/ul 13.9– 28.6% 
Number Abnormal 46 (<13.0 g/dl) 23 (<160 × 103/ul) 51 (>14.1%) 
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Within this population, there were two patients with TTP, and one with DIC. Four of the samples did not have detectable schistocytes upon visual inspection of the peripheral blood smear. There were 19 samples from 14 patients who had RBC fragment counts ≥ 0.04 × 106 cells/μl.

19 Specimens with RBC Fragments ≥ 0.04 × 106/ul

HemoglobinPlateletsRDW
Range 8– 14.1 g/dl 59– 906 × 103/ul 16.4– 25.3% 
Number Abnormal 15 (<13 g/dl) 4 (<160 × 103/ul) 19 (>14.1%) 
HemoglobinPlateletsRDW
Range 8– 14.1 g/dl 59– 906 × 103/ul 16.4– 25.3% 
Number Abnormal 15 (<13 g/dl) 4 (<160 × 103/ul) 19 (>14.1%) 
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The diagnoses in these 14 patients were iron deficiency anemia (4 patients), thalassemia trait (2), acute lymphoblastic leukemia (2), and one each with TTP, sickle cell anemia, heart failure, kidney stone, cerebrovascular accident (CVA), and end stage renal disease. We conclude that the RBC fragment flag on the ADVIA 2120 is nonspecific. Although it does detect schistocytes in TTP, these are often present in low numbers. Quantitatively, the most numerous RBC fragments are found in diseases with marked anisopoikilocytosis, such as iron deficiency anemia.

Topics:
acute lymphocytic leukemia, blood platelets, cerebrovascular accident, clinical diagnosis, erythrocytes, heart failure, hemoglobin, inspection, iron deficiency anemia, kidney calculi

Disclosure:Off Label Use: The RBC fragment flag is not FDA approved on the ADVIA 2120 hematology analyzer.

2007, The American Society of Hematology
2007
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