Specimen

Plasma

Collection Medium:

Alternate
Collection Media:

Call laboratory for additional acceptable specimen collection 
containers.

Minimum:

2 ml whole blood in light green top tube or 2 microtubes.  Do not draw 
before 6 hours after dose.

Testing Schedule:

24 hrs/day, 7 days a week, including holidays.

Analytic Time:

2 hours (upon receipt in laboratory)

Reference Range:

Therapeutic:  <2.1 ng/ml at 6 hours after dose in adults.

Critical value: >2.1 ng/ml (adults)

Comments:

Digibind (fab fragment) interferes with digoxin assay. Call lab for
details.

Test
Limitations:

The assay is unaffected by icterus (bilirubin is less than 65 mg/dl), 
hemolysis (Hb is less than 1 g/dl), lipemia (Intralipid is less than 
1500 mg/dl), and biotin is less than 100 ng/ml (criterion:  recovery 
within plus or minus 0.15 ng/ml at digoxin is less than 1.5 ng/ml, or 
within plus or minus 10% at digoxin levels is greater than 1.5 ng/ml).

No interference was observed from rheumatoid factor (RF is less than 
1630 IU/ml).  In patients receiving therapy with high biotin doses 
(i.e. is greater than 5 mg/day) no sample should be taken until at 
least 8 hours after the last biotin administration.

In vitro tests were performed on 69 commonly used pharmaceuticals.  No 
interference with the assay was found.

Digoxin-like immunoreactive substances (DLIS) have been identified in 
blood from patients in renal failure, liver failure, and pregnant women 
in their third trimester. Studies have shown that the presence of DLIS 
in a sample can result in a false elevation of digoxin when assayed by
commercially available immunoassay.(1-3)

The manufacturer of Digoxin Immune FAb (antibody fragment therapy) has 
stated that no immunoassay technique is suitable for quantitating 
digoxin in serum from patients undergoing this treatment.(4)

Uzara and Nabumetone may cause falsely elevated digoxin results.

As with all tests containing monoclonal mouse antibodies, erroneous 
findings may be obtained from samples taken from patients who have been 
treated with monoclonal mouse antibodies or have received them for 
diagnostic purposes. Digoxin contains additives which minimize these 
effects. In rare cases, interference due to extremely high titers of 
antibodies of streptavidin can occur.

(1) Keys PW, Stafford RW. In: Taylor WJ, Finn AL, eds. Individualizing
    Drug Therapy: Practical Applications of Drug Monitoring. New York,
    Gross, Townsend, Frank, Inc; 1981;vol 3:1-21.

(2) Valdes R Jr.: Clin Chem. 1985;31:1525-1532

(3) Valdiva R, Hornig Y, Gross S, Khayam-Bashi H: Digoxin-like
    Immunoreactive Factor Cross-reactivity in the CEDIA Digoxin R Assay
    on the RA-1000. Clin. Chem. 1990;36(6):1111

(4) Digibind Product Information. Burroughs Wellcome Co. Research
    Triangle Park. NC 1990

Methodology:

Electrochemiluminescence Immunoassay

CPT Code:

80162

See Additional Information:
Chemistry Critical Lab Values