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Test Code ADM13 ADAMTS13 Activity and Inhibitor Profile

Reporting Name

ADAMTS13 Activity and Inhibitor Profile

Useful For

Assisting with the diagnosis of congenital or acquired thrombotic thrombocytopenic purpura

Profile Information

Test ID Reporting Name Available Separately Always Performed
ADMFX ADAMTS13 Activity Assay No Yes
ADMIN ADAMTS13 Interpretation No Yes

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
ADMIS ADAMTS13 Inhibitor Screen No No
ADMBU ADAMTS13 Inhibitor Bethesda Titer No No

Testing Algorithm

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.

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Plasma Na Cit


Specimen Required


See Coagulation Studies in Special Instructions.

 

Specimen Type: Platelet-poor plasma

Collection Container/Tube: Light-blue top (citrate)

Submission Container/Tube: Plastic vials

Specimen Volume: 2 mL in 2 plastic vials each containing 1 mL

Collection Instructions:

1. Specimen must be drawn prior to replacement therapy.

2. Spin down, remove plasma, and spin plasma again.

3. Freeze specimens immediately at ≤-40° C, if possible.

4. Send specimens in the same shipping container.

Additional Information:

1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.

2. If priority specimen, mark request form, give reason, and request a call-back.

3. Each coagulation assay requested should have its own vial.

Forms:

1. Coagulation Patient Information (T675) in Special Instructions

2. If not ordering electronically, complete, print, and send a Coagulation Test Request Form (T753) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/coagulation-test-request-form.pdf)


Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma Na Cit Frozen 14 days

Reference Values

ADAMTS13 ACTIVITY ASSAY

≥70%

 

ADAMTS13 INHIBITOR SCREEN

Negative

 

ADAMTS13 BETHESDA TITER

<0.4 BU

Day(s) and Time(s) Performed

Monday through Sunday; Varies

Test Classification

See Individual Test IDs

CPT Code Information

85397-ADAMTS13 activity assay

85335-ADAMTS13 inhibitor screen assay (if appropriate)

85335-ADAMTS13 Bethesda titer (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ADM13 ADAMTS13 Activity and Inhibitor Profile In Process

 

Result ID Test Result Name Result LOINC Value
61211 ADAMTS13 Activity Assay 53622-7
34586 ADAMTS13 Interpretation 69049-5

Clinical Information

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.

Interpretation

<10% ADAMTS13 activity is highly indicative of thrombotic thrombocytopenic purpura (TTP) in an appropriate clinical setting. The presence of ADAMTS13 inhibition (positive inhibitor screen) with a measurable antibody titer is most consistent with an acquired TTP.

Clinical Reference

1. Sadler JE: Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura. Blood 2008 Jul 1;112(1):11-18

2. George JN: How I treat patients with thrombotic thrombocytopenic purpura: 2010. Blood 2010 Nov 18;116(20):4060-4069

3. Upshaw JD, Jr: Congenital deficiency of a factor in normal plasma that reverses microangiopathic hemolysis and thrombocytopenia. N Engl J Med 1978 Jun 15;298(24):1350-1352

Analytic Time

ADAMTS13 Activity Assay: 24 hours/ADAMTS13 Inhibitor Assay: 1-3 days/ADAMTS13 Bethesda Titer: 1-3 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild OK; Gross reject

Icterus

Mild OK; Gross reject

Other

NA

 

Method Name

ADMFX: Fluorescence Resonance Energy Transfer (FRET)

ADMIS, ADMBU: Mixing Studies