Today we’ll be discussing thrombotic thrombocytopenic purpura, or TTP , which is a serious blood disorder requiring immediate treatment with plasma exchange. TTP is often diagnosed based on the exclusion of other thrombotic microangiopathies.
Patients with TTP often present with symptoms including anemia, increased lactate dehydrogenase, and diminished ADAMTS13 activity. ADAMTS13 is a plasma enzyme required for processing the von Willebrand factor. Therefore, patients with TTP are at an increased risk for platelet thrombosis and organ tissue injury.
In suspected TTP patients, plasma exchange is usually started immediately, even before ADAMTS13 assay results are available.
Dr. Wu , who recently published an article in TRANSFUSION on the measurement of ADAMTS13 activity in TTP patients, comments:
“A key clinical question is whether the blood samples taken after the start of plasma exchange therapy are still effective for evaluating the patient’s ADAMTS13 activity level for diagnosis of TTP.”
In order to answer this question, Dr. Wu and his team followed a cohort of 19 acquired TTP patients receiving plasma exchange, and measured daily activity of ADAMTS13 using a novel SELDI-time of flight mass spectrometer -based method.
Dr. George , who wrote an editorial on the topic summarizes the results:
“In most patients, the severe ADAMTS13 deficiency persists in spite of plasma exchange for several days. And this allows clinicians to have a second chance to measure this activity if sample for ADAMTS13 activity had not been drawn before plasma exchange was begun.”
Dr. Wu and his team also found that recovery of ADAMTS13 activity within one week of daily plasma exchange was significantly associated with better patient prognosis. Patients with an ADAMTS13 activity that did not recover were more likely to have further TTP symptoms or die.
Dr. George cautions:
“The measurement of ADAMTS13 is not simple. Our experience has been that different assays for ADAMTS13 can give very different results in the same sample from the same patient.”
Dr. George also stresses that the diagnosis of TTP should not rely solely on laboratory results; the diagnosis requires clinical evaluation.
We’ll be back with another edition of Transfusion News on January 30th. Thanks for joining us.
References
1. George JN. Measuring ADAMTS13 activity in patients with suspected thrombotic thrombocytopenic purpura: when, how and why? Transfusion 2015;55:11-13.
2. Wu N, Liu J, Yang S, Kellett ET, Cataland SR, Li H, Wu HM. Diagnostic and prognostic values of ADAMTS13 activity measured during daily plasma exchange therapy in patients with acquired thrombotic thrombocytopenic purpura. Transfusion 2015;55:18-24.
Dr. George also stresses that the diagnosis of TPP should not rely solely on laboratory results; the diagnosis requires clinical evaluation.
this should read TTP, not TPP