A physician's office-based digoxin assay (Seralyzer) evaluated for interference by endogenous digoxin-like...

Area of Science:

• Clinical Chemistry
• Immunoassay Technology
• Pharmacokinetics

Background:

• Digoxin is a critical medication for heart conditions, requiring precise monitoring.
• Digoxin-like immunoreactive factors (DLIF) can interfere with digoxin testing, leading to inaccurate results.
• Physician's office laboratory (POL) analyzers need to be evaluated for accuracy and interference.

Purpose of the Study:

• To evaluate the Ames Seralyzer digoxin immunoassay for interference by DLIF.
• To compare the Seralyzer's performance with a known DLIF-detecting assay (Abbott TDx).
• To assess the impact of DLIF on digoxin measurements in various patient populations.

Main Methods:

• Sera from normal, renal, hepatic, pregnant, and neonatal patients were analyzed.
• Samples were tested using the Ames Seralyzer and Abbott TDx digoxin immunoassays.
• Interference was quantified by measuring apparent digoxin values and DLIF detection potency.

Main Results:

• Only 4.7% of non-digoxin patients showed apparent digoxin >0.2 ng/mL on the Seralyzer, versus 75% on the TDx.
• The TDx assay was 17-fold more potent in detecting DLIF from adrenal extracts compared to the Seralyzer.
• Digoxin presence reduced DLIF interference potency, particularly for the TDx assay.

Conclusions:

• The Ames Seralyzer demonstrates significantly less DLIF interference compared to the Abbott TDx.
• The Seralyzer provides reliable digoxin measurements, even in patients with potential DLIF.
• Reduced DLIF cross-reactivity in the presence of digoxin explains comparable results between assays for patients on digoxin.