Features of TTP:
(1) microangiopathic hemolytic anemia
(2) neurologic symptoms
(3) renal disease (azotemia, proteinuria or hematuria)
(4) fever
(5) thrombocytopenic purpura, with platelet count < 100,000 per µL
(6) exclusion of DIC, eclampsia, active malignancy, and vasculitis
Therapy:
(1) daily high volume plasma exchange (35 mL/kg), with increase to two times a day if platelet count and LDH did not improve
(2) corticosteroids, oral and intravenous
(3) aspirin and dipyridamole
Laboratory Testing:
(1) serum LDH (upper limit of normal 250 U/L)
(2) platelet count
(3) testing performed daily before plasmapheresis
(4) tapering of treatment begun when platelet count was > 150,000 per µL and the LDH was < 300 U/L and when both values were stable for at least 2 treatment days
LDH and platelet counts for days 0-2
No significant differences between survivors and nonsurvivors.
LDH and platelet counts for days 3-6
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Survivors
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Non-Survivors
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platelet count
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mean count 119,000 per µL on day 3; continued to increase to around 200,000 per µL by day 6
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mean count 46,000 per µL on day 3; remained relatively unchanged to day 6 with none rising above 75,000 per µL
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LDH
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show a decrease in level by day 3, with mean level 364 U/L; steadily decreased, with 71% reaching normal levels by day 6
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no decrease in level by day 3 with mean level 891 U/L; only 1 patient showed decreasing levels, 0% reached normal levels
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Interpretation:
• The area under the ROC curve for LDH levels increases earlier than the area for the platelet count ROC curve, indicating that LDH levels may indicate response earlier than the platelet count.
• Patients recognized on day 3 as belonging to the potential non-survivor group could benefit from more aggressive therapy, including splenectomy, intravenous immunoglobulin, or vincristine
Implementation Note:
• Analyzing the pattern of LDH and platelet levels over days 3-6 offers some challenges, particularly detecting relapse and distinguishing this from normal variability in results.
• Adding therapeutic decisions for when to stop treatment or to offer suggestions for more aggressive therapy could be considered.
