Methods for eliminating interferences in digoxin immunoassays caused by digoxin-like factors

Area of Science:

• Clinical Chemistry
• Immunoassay Development
• Biochemical Analysis

Background:

• Endogenous, circulating digoxin-like immunoreactive factors (DLIF) interfere with accurate serum digoxin quantification.
• Cross-reactivity with antisera in digoxin assays complicates measurement.
• Need for methods to mitigate DLIF interference in clinical diagnostics.

Purpose of the Study:

• To investigate methods for decreasing or removing DLIF interference in digoxin immunoassays.
• To assess the efficacy of prolonged incubation and ultrafiltration for DLIF removal.
• To evaluate the impact of these methods on the accuracy of digoxin measurement.

Main Methods:

• Investigated prolonged assay incubation times (60 min vs. 30 min).
• Employed ultrafiltration as a method to remove DLIF based on serum protein-binding.
• Compared ultrafiltration with heat- or acid-precipitation for DLIF removal.
• Conducted analytical-recovery studies using true digoxin.

Main Results:

• Prolonging incubation decreased apparent digoxin concentrations (DLIF) by an average of 68%.
• Ultrafiltration removed approximately 90% of DLIF from serum.
• Ultrafiltration demonstrated adequate recovery (>95%) of true digoxin for clinical use.
• Heat- or acid-precipitation were less effective in removing DLIF.

Conclusions:

• Optimized incubation times and ultrafiltration significantly minimize DLIF interference in digoxin immunoassays.
• Ultrafiltration is a viable and effective method for removing DLIF in routine clinical settings.
• These techniques enhance the reliability of serum digoxin quantification.