ADAMTS13 ACTIVITY AND INHIBITOR PROFILE (ADA13B)

Message
This test code used for inpatients only. (For outpatients, use test code A13ARI.) Test performed by Mayo Medical Laboratories.
CPT code 85397 will also be used if the inhibitor screen and/or titer are needed.

Test Code
LAB8554

CPT Codes
85397

Includes
Testing begins with ADAMTS13 activity assay to evaluate the percent activity. If the ADAMTS13 activity assay is <30%, an inhibitor screen will be performed to look for specific ADAMTS13 inhibition. If specific inhibition is apparent, the titer of the inhibitor will be determined

Preferred Specimen
2 mL plasma in light blue top tube

Transport Container
2 plastic vials, each containing 1 ml of plasma

Transport Temperature
Frozen

Specimen Stability
14 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis, lipemia, or icterus

Limitations
Interferences of ADAMTS13 activity assay include high levels of endogenous von Willebrand factor, hyperlipidemia, hemolysis with plasma free hemoglobin >2 g/L, hyperbilirubinemia (bilirubin concentration >100 micromolar), and cleavage by other protease. Recent plasma exchange or transfusion may falsely normalize ADAMTS13 levels, thus potentially masking the diagnosis of TTP

Reference Range
ADAMTS13 ACTIVITY ASSAY:  > or =70%
ADAMTS13 INHIBITOR SCREEN: Negative
ADAMTS13 BETHESDA TITER:  <0.4 BU

Clinical Significance
Thrombotic thrombocytopenic purpura (TTP), a rare (estimated incidence of 3.7 cases per million) and potentially fatal thrombotic microangiopathy (TMA) syndrome, is characterized by a pentad of symptoms: thrombocytopenia, microangiopathic hemolytic anemia (intravascular hemolysis and presence of peripheral blood schistocytes), neurological symptoms, fever, and renal dysfunction. The large majority of patients initially present with thrombocytopenia and peripheral blood evidence of microangiopathy, and in the absence of any other potential explanation for such findings, satisfy criteria for early initiation of plasma exchange, which is critical for patient survival. TTP may rarely be congenital (Upshaw-Shulman syndrome), but far more commonly is acquired. Acquired TTP may be considered to be primary or idiopathic (the most frequent type) or associated with distinctive clinical conditions (secondary TTP) such as medications, hematopoietic stem cell or solid organ transplantation, sepsis, and malignancy. The isolation and characterization of an IgG autoantibody frequently found in patients with idiopathic TTP, clarified the basis of this entity and led to the isolation and characterization of a metalloprotease called ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 motif 13 repeats), which is the target for the IgG autoantibody, leading to a functional deficiency of ADAMTS13. ADAMTS13 cleaves the ultra high-molecular-weight multimers of von Willebrand factor (VWF) at the peptide bond Tyr1605-Met1606 to disrupt VWF-induced platelet aggregation. The IgG antibody prevents this cleavage and leads to TTP. Although the diagnosis of TTP may be confirmed with ADAMTS13 activity and inhibition studies, the decision to initiate plasma exchange should not be delayed pending results of this assay.

Performing Laboratory
Mayo Medical Laboratories



The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.