MORL ADAMTS-13 Activity
Label Mnemonic: MADAM
Epic Lab Code: LAB8450
Downtime Form: A-1a Miscellaneous Request
Commercial Mail-out Laboratory
5231 RCP
356-8593
Specimen(s):
Plasma
Collection Medium:
Light Blue top tube 2.7 mL (Na Citrate)
Minimum:
Preferred Minimum: 1 mL frozen citrated plasma
Absolute Minimum: 0.5 mL frozen citrated plasma
Delivery Instructions:
Deliver to laboratory immediately after collection. Critical frozen.
Testing Schedule:
Testing performed Monday - Friday ONLY (No weekend or holiday service)
Turn Around Time:
24 hours upon receipt at reference laboratory
NOTE: For same day service sample must be collected by 12:00 noon.
Reference Range:
Normal (>60%); Reduced (10%-60%); Depleted (<10%)
Interpretive Data:
ADAMTS-13 Activity Assay: This assay is based on the fluorescence energy transfer (FRET) technology. A synthetic fragment of the von Willebrand Factor protein is used as substrate. Cleavage of the substrate between two modified residues relieves fluorescence quenching capabilities. The assay quantifies the amount of the fluorescence released when the substrate is cleaved by ADAMTS-13. Average normal activity is set at 100%.

Limits of testing methodology: The assay utilizes short vWF peptide as substrate which lacks exosites for ADAMTS-13 interaction.
Comments:
Thrombotic thrombocytopenic purpura:
Thrombotic thrombocytopenic purpura (TTP) is an ultra-rare disease caused by platelet clumping on aggregated unusually large von Willebrand factor (vWF) multimers, leading to microthrombi formation in small blood vessels and potentially culminating in multi-organ failure. In healthy individuals, ADAMTS13, a circulating protease, specifically cleaves large vWF multimers, significantly reducing platelet thrombi formation under high shear stress. Reduced ADAMTS13 activity (<60%) can be found in the acquired form of TTP in association with ADAMTS13 autoantibodies. ADAMTS13 activity is totally absent (<10%) in the inherited form of TTP, which is known as Upshaw- Schülman syndrome.

Atypical hemolytic uremic syndrome:
Atypical hemolytic uremic syndrome (aHUS) is another ultra-rare thrombotic microangiopathy. Although ~50% of cases of aHUS are caused by mutations in genes in the alternative complement pathway, about 60% of aHUS patients are estimated to have reduced ADAMTS13 activity (<60% of normal but above 10% of normal) (1). Whether reduced ADAMTS13 activity is an important component of the aHUS phenotype has not been determined.

Indications for screening: Screening is appropriate for patients with TTP and aHUS.

Reference: Feng S, et al.: Partial ADAMTS13 deficiency in atypical hemolytic uremic syndrome. Blood. 2013 Aug 22;122(8):1487-93. Epub 2013 Jul 11.
Methodology:
Fluorescence Resonance Energy Transfer (FRET)
CPT Code:
85397