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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

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DIGOXIN

Item Value
Available Stat? Yes
Test code DIG
Performed by? Chemistry
Sendout? no
Price range $$
In House Availability Routine: 7 days
Stat: 24 hours/7 Days
Principle The Siemens Centaur assay is a competitive immunoassay using a direct chemiluminescent technology.
Interpretation Useful for assessing toxicity in therapy for CHF and cardiac arrhythmia.

Symptoms of toxicity include nausea, vomiting, delirium and green/yellow visual disturbance. Cardiac signs of toxicity include ST segment abnormality, multiform PVC's, bigeminy V-tach and V-fib, paroxysmal atrial tachycardia and AV block.

In acute toxic ingestion vomiting, bradycardia and hyperkalemia are seen. Serum K+ and ECG monitoring are useful for rapid assessment of severe toxicity before digoxin concentration is available. Toxicity manifested by AV block often occurs at significantly lower concentrations than toxicity manifested by ectopy.

A variety of medications and conditions can affect serum concentrations:

1. Increase: Quinidine, verapamil, nifedipine, amidorone, spironolactone, renal insufficiency, and decrease GI motility.

2. Decrease: Cholestyramine, antacids, increased GI motility, high fiber diet and hyperthyroidism.
Container type gold top gel tube
Amount to Collect 2 mL
Sample type Blood
Special instructions Plasma samples cannot be assayed.

Blood sample should be obtained 8 - 24 hours after last dose of digoxin or no less than 4 hours after last IV dose to avoid non-equilibrated (non-steady state, pre-distributional) sampling. Specimen collection time must be noted on the requisition form.
Normal range 0.5-2.0 mcg/L (0.6-2.6 nmol/L)
All values > 2.0 mcg /L (> 2.6 nmol/L) are considered Critical Values and are called to the physician or patient care unit immediately.
Stability Specimen is stable 48 hours at 2 - 8°C; 2 months at -20°C.
Interferences 1. The sera from patients in specific populations (i.e. patients with renal and/or hepatic failure, newborn infants and pregnant women) have been reported to contain an unidentified component that may produce positive results for digoxin, even when no drug is present.

2. Serum from patients treated with anti-digoxin Fab fragments (Digibind(R)) cannot be assayed. False low or high results may occur. Call the Laboratory Medicine Resident in Clinical Chemistry (x65527 or pager 415-443-2311) to discuss appropriate monitoring following administration of Digibind.

3. Auto- (rheumatoid factor) and heterophile antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays. Patients routinely exposed to animals or to animal serum products can be prone to this interference. Anomalous values, spuriously low or high, may be observed. Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).
References 1. Bayer 111798 Rev. C, 5/2000. Siemens Medical Solutions Diagnostics, Malvern, PA.

2. Henry, J.B.: Clinical Diagnosis and Management by Laboratory Methods, 20th ed, Philadelphia, W.B. Saunders Co., p. 349-350; 2001.

3. Rainey, Petrie: Effects of digoxin immune Fab (Ovine) on digoxin immunoassays. American Journal of Clinical Pathology 1990.

4. Tietz, N.W. Textbook of Clinical Chemistry and Molecular Diagnosis, ed. 4. St. Louis, MO: Elsevier Saunders, 1256-1257; 2006.

5. Young, DS. Effects of Drugs on Clinical LaboratoryTests. Ed. 4. Washington D.C.: AACC Press; 1995.
CPT coding 80162
Last Updated 6/18/2011 8:30:09 AM
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