Endogenous digoxin-like immunoreactivity in elderly patients with normal serum creatinine concentrations

Area of Science:

• Clinical Chemistry
• Pharmacology
• Geriatrics

Background:

• Digoxin is a critical medication for heart conditions.
• Digoxin-like immunoreactive substance (DLIS) can interfere with digoxin assays.
• Assessing DLIS impact in elderly patients with normal renal function is important.

Purpose of the Study:

• To investigate the effect of DLIS on serum digoxin measurements in elderly patients.
• To compare digoxin assay results using two different radioimmunoassays with varying DLIS cross-reactivity.
• To determine if DLIS affects digoxin level accuracy in elderly individuals with normal creatinine.

Main Methods:

• Studied elderly (>70 years) and younger (<55 years) patients with normal serum creatinine (≤1.5 mg/dL).
• Used two radioimmunoassays: RIANEN (detects DLIS) and Immophase (low DLIS cross-reactivity).
• Compared apparent digoxin concentrations in patients receiving and not receiving digoxin, analyzing DLIS levels and creatinine clearance.

Main Results:

• No DLIS was detected in patients not receiving digoxin.
• For patients on digoxin, most measured levels were within the therapeutic range.
• No significant difference in digoxin concentrations was found between RIANEN and Immophase assays in young or elderly patients without renal/liver failure.
• Decreasing creatinine clearance did not significantly increase the difference between assay results.

Conclusions:

• DLIS does not compromise serum digoxin measurements in elderly patients with normal serum creatinine.
• Both RIANEN and Immophase assays provide reliable digoxin level determinations in this population.
• The study supports accurate therapeutic drug monitoring of digoxin in older adults with preserved renal function.