ADAMTS 13 Inhibitor (test performed if activity level <30%)

Also Known as (Alias) ATS-13 Inhibitor
Indications TTP
Method Flourescence Resonance Transfer Assay (FRET)
Test Information If ADAMTS13 activity is less than 30%, then reflex testing for an inhibitor and antibody will be performed.  The FRET assay is repeated using a 1:1 mix of normal pooled plasma and heat inactivated patient’s plasma. If the activity results are below the expect activity then the results are reported as a percent inhibition.  Inhibition results of greater than 32% is considered positive in our assay.
Additional Test Information Strong antibody-mediated inhibition of ADAMTS13 activity (>90%) is seen in approximately half of the patients with acquired TTP. The presence of this level of inhibition strengthens the case for a diagnosis of TTP. The significance of milder ADAMTS13 inhibition is unclear, particularly when the overall ADAMTS13 level is not severely depressed. The assay used does not distinguish between antibody-mediated and non-specific ADAMTS13 inhibition.

Caution should be exercised in the interpretation of any assay for ADAMTS13; the results should only be considered in the conjunction with the patient’s clinical condition. Previous transfusion, plasma infusion, plasma exchange, or free hemoglobin in the plasma (>2g/L) may affect the level of ADAMTS13 as well as any inhibitors that are present.

Sample Requirements Citrate (blue top)
Requested Volume 5cc Citrate (blue top)
Shipping Information Ship to Bloodworks immediately after draw to ensure the laboratory receives specimen within 4 hours of draw time.  If this is not possible, spin within 4 hours and freeze plasma at -20C,  then ship frozen specimen on dry ice.

NOTE: If the sample is received as whole blood after 4 hours of draw time, the sample will need to be redrawn

Send samples to:
Bloodworks Northwest
Attn:  Platelet Immunology Lab, Rm 619
921 Terry Avenue
Seattle, WA 98104

For additional information, please see Ordering Information

Requisition Form RFT- Platelet Immunology Laboratory
RFT- Hemostasis Reference Laboratory
Transaction Code 3260-02
CPT Codes 85335
Test Schedule Reflexive
Turn around Time (analytic time) 2-3 business days
Report/Results Fax number required to receive report

Your gift of blood, time or money saves lives.