Adult patient:
Clotted blood tube
(Serum gel separator clot activator tube)
Minimum blood volume: 5 mL
Paediatric patient:
Paediatric clotted blood tube
Number of vials: 2
Minimum blood volume: 1.6 mL
Authorisation code required
No
24 Hr available service
No
For suspected digoxin overdose cases, please call Duty Biochemist for 'Urgent' digoxin level testing.
Precaution
Sample should preferably be collected 6 - 8 Hr after drug administration.
Method
Immunoassay
Reference interval
Therapeutic range: 1.2 - 2.6 nmol/L
(Source: from manufacturer's kit insert)
Target therapeutic range for patients with heart failure is 0.6 - 1.3 nmol/L
(J Am Coll Cardiol 2009; 14:e1 - e90).
Digoxin toxicity can be potentiated by hypokalaemia. Please interpret result with potassium level.
Clinical indication
Assessment of suspected digoxin toxicity or inadequate response
Result interpretation
The therapeutic interval is approximate, toxicity can occur at lower levels, especially if there is associated hypokalaemia (please interpret result with potassium level). Other factors to consider when evaluation the correct therapeutic dosage for each patient include age, thyroid function, acid-base balance, hypoxia, renal function and other clinical factors.
For therapeutic drug monitoring, blood should be collected > 6 Hr after last digoxin dose; otherwise, spuriously high result may be obtained.
Digoxin half-life is 20 - 50 hours; prolonged with renal impairment.
Measurement of uncertainty
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.
The manufacturer of DIGIBIND (digoxin immune FAb (antibody fragment therapy)) has stated that no immunoassay technique is suitable for quantitating digoxin in serum from patients undergoing this treatment.
For patients receiving DIGIBIND therapy, digoxin result will be overestimated and patients should be monitored clinically (Clin Chem. 2002; 48(9): 1580-4) (Am J Crit Care. 2010; 19(4): 387-91). Please note that elimination of digoxin following DIGIBIND therapy can be further prolonged in patients with renal dysfunction (Ann Intern Med. 1993; 119(4): 273-7).
Uzara and Nabumetone may cause falsely elevated digoxin results.
Frequency of measurement
Daily