Digoxin, Free (Sendout)

General Information

Lab Name

Digoxin, Free

Lab Code

RFDIGG

Epic Name

Digoxin, Free (Sendout)

External Test Id

FRDIG

Description

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
Monitoring patients with possible digoxin-like immunoreactive factors (DLIFs)

Patient Preparation: For 12 hours before specimen collection, patient should refrain from taking multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Collection Timing: Collect blood 6 to 8 hours after last dose of digoxin.

References

Mayo Clinical & Interpretive Information: Digoxin, Free, Serum

Synonyms

FRDIG

Components

Code	Name
RFDIGR	Digoxin, Free

Interpretation

Method

Ultrafiltration followed by Electrochemiluminescent Immunoassay

Reference Range

See individual components

Ref. Range Notes

Reference Values:

Therapeutic Range, <16 years:	Therapeutic ranges have not been established for patients who are under 16 years of age.
Therapeutic Range, >16 years:	0.4-0.9 ng/mL
Toxic Range:	> or =3.0 ng/ mL

Interpretation:

The target therapeutic level is 0.4 to 0.9 ng/mL. Toxicity may be seen when free digoxin concentrations are 3.0 ng/mL or higher. Pediatric patients may tolerate higher concentrations.

Therapeutic concentrations for free digoxin are 25% lower than therapeutic values for total digoxin due to the separation of protein-bound digoxin in the assay.

Interferences and Limitations

Cautions:

Patients vary in their responsiveness to digoxin.

Renal dysfunction alters the metabolism of digoxin and antibody-bound digoxin.

It takes 6 to 8 hours after digoxin administration for equilibration between serum and tissue; results obtained from specimens collected less than 6 to 8 hours after the last dose of digoxin should be interpreted with caution.

Digibind (Glaxo Wellcome, Research Triangle Park, NC) is the most common brand of antidigoxin Fab fragments used; other brands are available and may be monitored by this assay.

References

Mayo Clinical & Interpretive Information: Digoxin, Free, Serum

Ordering & Collection

Specimen Type: Blood
Collection: 3 mL blood in RED TOP tube or GOLD SST

Collection Timing: Draw blood 6 to 8 hours after last dose of digoxin.
Handling Instructions: Outside Laboratories: Centrifuge sample and aliquot serum into a separate plastic vial within 2 hours of collection. Refrigerate serum while awaiting shipment. Transport with a cold pack.

Stability: Refrigerated (preferred): 7 days; Frozen: 180 days; Ambient: Unacceptable.

Reject Due To: Gross hemolysis.
Quantity: Requested: 1 mL serum
Minimum: 0.5 mL serum

Processing

Receiving Instructions

Centrifuge sample and aliquot serum into a separate plastic vial within 2 hours of collection. Refrigerate serum.

Sendouts:

Order Mayo Test: FRDIG
Interfaced: Yes [Interface: 601; Worksheet: MARF]

Stability: Refrigerated (preferred): 7 days; Frozen: 180 days; Ambient: Unacceptable.

Reject Due To: Gross hemolysis.

Misc Sendout

Performance

Lab Department

Sendouts Mayo Lab (RF)(MARF)

Frequency

Performed: Monday through Sunday. Reported: 1 day from sample receipt at Mayo Clinic Labs.

Available STAT?

Performing Location(s)

Sendout	Mayo Clinic Laboratories 800-533-1710 200 First Street Southwest Rochester, MN 55901

Billing & Coding

CPT Codes: 80163
LOINC: 3562-6