Diagnostic and prognostic values of ADAMTS13 activity measured during daily plasma exchange therapy in patients with acquired thrombotic thrombocytopenic purpura.

BACKGROUND: Thrombotic thrombocytopenic purpura (TTP) requires immediate treatment with plasma exchange (PE) to prevent disease mortality and/or morbidity. Frequently, PE is initiated before blood sample is collected to confirm ADAMTS13 deficiency. However, the effect of PE treatments on the evaluation of ADAMTS13 is uncertain. Moreover, the pertinence of ADAMTS13 activity during PE therapy to prediction of treatment outcomes is unclear. Thus, clarification of the diagnostic and prognostic values of ADAMTS13 activity obtained during PE treatment is an unmet clinical need. STUDY DESIGN AND METHODS: A total of 212 sequential samples were obtained during the course of daily PE treatment from 19 patients with acquired TTP. ADAMTS13 activity levels were determined in these longitudinal samples for analysis.
RESULTS: After the initial three daily PE procedures, the sensitivities of ADAMTS13 activity in diagnosis of TTP (<10%) were 89, 83, and 78%, respectively. To determine prognostic value, patients with (n = 7) and without (n = 12) a recovery of ADAMTS13 activity to more than 10% within seven sessions of daily PE treatment were compared. Recovery of ADAMTS13 activity to more than 10% within 7 days is significantly associated with a timely achievement of clinical response (p < 0.01). In contrast, the patients without more than 10% ADAMTS13 within 1 week appear at risk for worse treatment outcomes manifested as TTP exacerbation, treatment refractoriness, or death.
CONCLUSION: The data suggest that ADAMTS13 activities measured during the initial period of PE therapy offer both diagnostic and prognostic values in acquired TTP.