A simple, automated, nonextraction assay for serum digoxin using particle-enhanced immunoassay

Area of Science:

• Clinical Chemistry
• Immunochemistry
• Analytical Chemistry

Background:

• Serum digoxin monitoring is crucial for therapeutic drug management.
• Existing immunoassays may have limitations in speed, sensitivity, or interference.
• Latex particle-enhanced immunoassays (LPEIA) offer potential for rapid diagnostics.

Purpose of the Study:

• To adapt and validate a latex particle-enhanced immunoassay for serum digoxin quantification on a centrifugal analyzer.
• To assess the assay's performance characteristics, including speed, recovery, precision, and interference.
• To compare the developed assay with an established fluorescence polarization immunoassay (FPIA).

Main Methods:

• Adaptation of a digoxin-coated latex particle immunoassay for automated centrifugal analysis.
• Use of a small serum sample volume (4 microliters) without pretreatment.
• Measurement of inhibition of antibody-induced particle aggregation.
• Comparison with a gold-standard fluorescence polarization immunoassay (FPIA).

Main Results:

• Assay completion time of 10 minutes.
• Mean analytical recovery of 98.1%.
• Intra-assay precision < 4.2% and inter-assay precision < 15.0%.
• High correlation with FPIA (R = 0.97).
• No significant interference observed from digoxin-like immunoreactive compounds in chronic renal failure patients.

Conclusions:

• The adapted LPEIA is a rapid, accurate, and precise method for serum digoxin measurement.
• The assay demonstrates good performance and minimal interference, suitable for routine clinical use.
• This particle-enhanced turbidimetric inhibition immunoassay (PETINIA) represents an advancement in LPEIA sensitivity for serum matrices.