Radioimmunoassay for digoxin with a fully automated continuous-flow system

Area of Science:

• Clinical Chemistry
• Immunoassay Technology
• Analytical Chemistry

Background:

• Radioimmunoassays (RIA) are crucial for therapeutic drug monitoring.
• Traditional RIAs can be time-consuming and labor-intensive.
• Automation is key to improving efficiency and precision in diagnostic assays.

Purpose of the Study:

• To develop and validate a fully automated, continuous-flow radioimmunoassay for digoxin.
• To assess the performance characteristics of the automated digoxin assay.
• To compare the automated method with an established manual assay.

Main Methods:

• Utilized a Technicon AutoAnalyzer system for automated reagent dispensing and sample handling.
• Employed antibodies linked to magnetizable particles for rapid separation of bound and free fractions using a magnet.
• Implemented non-equilibrium conditions due to precise timing and small incubation volumes (approx. 160 µL).

Main Results:

• Achieved a sample throughput of 30 samples per hour, with individual sample assay time of 15 minutes.
• Demonstrated high precision with a between-assay coefficient of variation <3% for digoxin concentrations between 1-3 µg/L.
• Established a standard curve range of 0.5-8.0 µg/L and showed no significant carryover between samples.
• Reported a high correlation (r = 0.969) with an established manual radioimmunoassay using charcoal separation.

Conclusions:

• The automated continuous-flow radioimmunoassay for digoxin is a rapid, precise, and efficient method.
• This automated assay offers significant advantages in terms of speed and throughput compared to manual methods.
• The method provides reliable digoxin quantification, suitable for clinical laboratory use.