Bethesda Assay for Factor 8
Abbrev Code: | BETH2 | ||
Order Code: | LAB3317 | Order Name: | Bethesda for Factor 8 |
Synonyms: | Factor 8 Hemophilia Antibody; Factor 8 Inhibitor; Hemophilia A Inhibitor; Bethesda Assay for Factor VIII | ||
Methodology: | Measurement of residual Factor 8 on mixtures of patient plasma mixed with normal pooled plasma. Factor 8 Bethesda samples are incubated for 2 hours at 37 C. | ||
CPT Codes: | 85335 x1, 85335 x1 | ||
Turnaround Time: | Specimen is accepted and processed 24 hours/day, 7 days/week. Test is performed as needed; results are reported within 2-4 days. | ||
Special Instructions: | Indicate on request form when the last Factor 8 infusion was administered. If Thrombin Time is >60 seconds. Bethesda Assay for Factor 8 will be cancelled with the following comment: SPECIMEN CANCELLED, INTERFERING SUBSTANCES DETECTED. CORRELATION WITH MEDICATIONS RECOMMENDED. | ||
Associated Links: | Specimen Collection and Processing for Coagulation Specimens |
Collection Instructions
Specimen: | Blood |
Optimal Volume: | Three 3 mL tubes, each containing 2.7 mL blood; each filled to fill line on tube. |
Minimum\Peds Volume: | Two 3 mL tubes, each containing 2.7 mL blood; each filled to fill line on tube. |
Container: | THREE Blue Na Citrate, 3.2% - fill to fill line on tube |
Collection Instructions: | See link to Specimen Collection and Processing of Coagulation Specimens. |
Causes for Rejection: | Underfilled tubes, overfilled tubes, clotted specimens, not received or processed and frozen within 4 hours of collection or, specimen thawed during transit. Patients on Hemlibra® (emicizumab) |
Contraindications: | Factor 8 infusion within last week |
Processing and Shipping
Specimen Processing: |
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Shipping Instructions: |
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Test Performed at or Referral Lab | UM Special Coag (K) (UMMC East Bank) |
Interpretive
Reference Range: | 0 Bethesda U/mL |
Use: | The Bethesda assay is designed specifically to measure the concentration of anti-Factor 8 antibody in patients with hemophilia A. One Bethesda Unit is the amount of antibody that will inactivate 0.5 U/mL (50%) of Factor 8. Patients with "spontaneous" (acquired) antibodies will give variable results because of the unique conditions of the test and the nature of these types of antibodies. |
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