Bethesda Assay for Factor 8
| Sunquest Code: | BETH2 | ||
| Epic Code: | LAB3317 | Epic 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. | ||
| 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 |
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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 or clotted specimens. Patients on Hemlibra® (emicizumab) |
| Contraindications: | Factor 8 infusion within last week |
Processing and Shipping
| Specimen Processing: | See link to Specimen Collection and Processing for Coagulation Specimens. |
| Shipping Instructions: | See link to Specimen Collection and Processing for Coagulation Specimens. |
| Test Performed at or Referral Lab | Special Coagulation (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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