Algorithm for diagnosis and early management of TTP based on the availability of a rapid ADAMTS13 activity assay. Our approach to the incorporation of rapid ADAMTS13 activity assays for the diagnosis and early management of TTP is shown. First, an assessment for alternative etiologies of TMAs is completed. If no clear alternative is identified, a risk assessment score such as the PLASMIC score should be calculated. For cases of intermediate and high risk for TTP, diagnosis and early management depends on the presence of a highly accurate (≥95% sensitivity and specificity) rapid ADAMTS13 assay such as the HemosIL AcuStar CLIA. If a rapid assay is available, empiric management may be deferred until the result is available. If no rapid assay is available, empiric therapy is initiated while awaiting the results of a reference standard ADAMTS13 activity assay. This algorithm represents general clinical guidance, but does not replace the need for clinical judgment and individualized management.