Digoxin, Free, Serum
Use
This test is useful for evaluating recrudescent (breakthrough) digoxin toxicity in renal-failure patients, assessing the need for more antidigoxin Fab to be administered, deciding when to reintroduce digoxin therapy, and monitoring patients with possible digoxin-like immunoreactive factors (DLIFs). Digoxin, a widely prescribed cardiac drug, has a narrow therapeutic window and excess can lead to severe side effects such as cardiac dysrhythmias, heart failure, seizures, and even death. Free digoxin assays help manage patients WHO have received digoxin-specific Fab fragment therapy, as traditional assays cannot distinguish between free and bound digoxin, leading to potentially misleading results.
Special Instructions
For 12 hours before specimen collection, patients should refrain from taking multivitamins or dietary supplements containing biotin (vitamin B7), commonly found in hair, skin, and nail supplements and multivitamins. Blood should be drawn 6 to 8 hours after the last dose of digoxin to ensure accuracy in results.
Limitations
Patients vary greatly in their response to digoxin, and renal dysfunction can substantially affect the metabolism and clearance of digoxin as well as its binding with antibodies. Results obtained from specimens collected less than 6 to 8 hours post-digoxin dosage should be interpreted with caution due to possible non-equilibrium. The presence of digoxin-like immunoreactive factors (DLIFs) can also interfere with testing, making it challenging to obtain accurate results in some cases. Clearance of Fab fragments may be delayed in renal failure patients, possibly leading to toxicity recurrence, emphasizing the need for careful monitoring.
New York Approved
Methodology
Immunoassay (ECLIA)
Biomarkers
LOINC Codes
- 3562-6
- 3562-6
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.6 mL
Container
Plastic vial; Preferred: Serum gel, Acceptable: Red top
Collection Instructions
Serum gel tubes should be centrifuged within 2 hours of collection. Red-top tubes should be centrifuged and serum aliquoted into a plastic vial within 2 hours of collection.
Patient Preparation
Do not take multivitamins or dietary supplements containing biotin for 12 hours prior to specimen collection.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | 7 days |
| Frozen | 180 days |