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EPIC CODE: LAB5323 ADAMTS13 Activity and Inhibitor Profile, Plasma

Additional Codes

Sunquest:      ADM13M
Mayo:            ADM13
Previously:    0030056

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 the ADAMTS-13 activity assay to evaluate the percent activity. If the ADAMTS-13 activity is less than 30%, an inhibitor screen will be performed to look for specific ADAMTS-13 inhibition. If specific inhibition is apparent, the titer of the inhibitor will be determined.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Plasma Na Cit

Shipping Instructions

Send both vials in the same shipping container.

Specimen Required

Patient Preparation: Fasting preferred

Collection Container/Tube: Light-blue top (3.2% sodium citrate)

Submission Container/Tube: Plastic vials

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

Collection Instructions:

1. Specimen must be collected prior to replacement therapy.

2. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing

3. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.

4. Aliquot plasma (1 mL per aliquot) into 2 separate plastic vials, leaving 0.25 mL in the bottom of centrifuged vial.

5. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, below -40° C.

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.

Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Na Cit Frozen 14 days

Reference Values








<0.4 BU

Day(s) Performed

Monday through Friday, Sunday

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


85335 (if appropriate)

85335 (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ADM13 ADAMTS13 Activity and Inhibitor Profile 53622-7


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 syndrome, is characterized by a pentad of symptoms: thrombocytopenia, microangiopathic hemolytic anemia (intravascular hemolysis and presence of peripheral blood schistocytes), neurological symptoms, fever, and kidney dysfunction. A 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 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 ADAMTS-13 (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 ADAMTS-13. ADAMTS-13 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 ADAMTS-13 activity and inhibition studies, the decision to initiate plasma exchange should not be delayed pending results of this assay.


Less than 10% ADAMTS-13 activity is highly indicative of thrombotic thrombocytopenic purpura (TTP) in an appropriate clinical setting. The presence of ADAMTS-13 inhibition (positive inhibitor screen) with a measurable antibody titer is most consistent with an acquired TTP.


This ADAMTS-13 activity assay is an in vitro assay using a synthetic substrate peptide in a static liquid environment. The measured ADAMTS-13 activity may not reflect the true in vivo biological ADAMTS-13 activity.


Not all patients with a clinical diagnosis of idiopathic thrombotic thrombocytopenic purpura (TTP) have a severe ADAMTS-13 deficiency. Conversely, patients with other non-TTP conditions may have a severe ADAMTS-13 deficiency (≤10%). These conditions include hemolytic uremic syndrome, hematopoietic stem cell and solid organ transplantation, liver disease, disseminated intravascular coagulation, sepsis, pregnancy, and certain medication. Therefore, TTP remains a clinical diagnosis.


Interferences of the ADAMTS-13 activity assay include high levels of endogenous von Willebrand factor, hyperlipidemia, hyperbilirubinemia (bilirubin concentration >30mg/dL), and cleavage by other proteases.


Recent plasma exchange or transfusion may falsely normalize ADAMTS-13 levels, thus potentially masking the diagnosis of TTP.


The impact of ADAMTS-13 levels and presence of inhibitors on overall survival, ultimate clinical outcome, responsiveness to plasma exchange, and relapse are still controversial. Therefore, clinical correlation is recommended.

Clinical Reference

1. Sadler JE: Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura. Blood. 2008 Jul 1;112(1):11-18. doi: 10.1182/blood-2008-02-078170

2. George JN: How I treat patients with thrombotic thrombocytopenic purpura: 2010. Blood. 2010 Nov 18;116(20):4060-4069. doi: 10.1182/blood-2010-07-271445

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. doi: 10.1056/NEJM197806152982407

4. Chiasakul T, Cuker A: Clinical and laboratory diagnosis of TTP: an integrated approach. Hematology Am Soc Hematol Educ Program. 2018 Nov 30;2018(1):530-538. doi: 10.1182/asheducation-2018.1.530

Method Description

The ADAMTS-13 activity is measured by a fluorescence resonance energy transfer based assay using a synthetic fragment of von Willebrand factor as substrate and quantifying the cleavage of this small fragment by the ADAMTS-13 protease. The inhibitor screen and titer assay are performed using mixing studies that are similar to the Bethesda assay. One inhibitor (Bethesda) unit is defined as the concentration of an inhibitor that is able to reduce ADAMTS-13 activity of normal pooled plasma by 50%.(Mackie I, Mancini I, Muia J, Kremer Hovinga J, Nair S, Machin S, Baker R. International Council for Standardization in Haematology (ICSH) recommendations for laboratory measurement of ADAMTS13. Int J Lab Hematol. 2020 Dec;42(6):685-696. doi: 10.1111/ijlh.13295)

Report Available

1 to 3 days

Specimen Retention Time

7 days

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

NY State Approved


Method Name

Fluorescence Resonance Energy Transfer (FRET)


1. Coagulation Patient Information (T675)

2. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Coagulation Test Request (T753)

-Renal Diagnostics Test Request (T830)

Secondary ID