Evaluation of the Bactec serum gentamicin assay

Area of Science:

• Clinical Chemistry
• Analytical Chemistry
• Pharmacology

Background:

• Gentamicin is an aminoglycoside antibiotic requiring therapeutic drug monitoring.
• Radioimmunoassay (RIA) is an established method for quantifying gentamicin levels.
• Accurate gentamicin measurement is crucial for optimizing efficacy and minimizing toxicity.

Purpose of the Study:

• To compare the precision and correlation of a radiometric assay with a standard radioimmunoassay for gentamicin quantification.
• To evaluate the suitability of the radiometric assay as an alternative method.

Main Methods:

• A radiometric assay for gentamicin was developed and compared against a radioimmunoassay protocol.
• Precision was assessed using coefficients of variation (CV) for within-run, day-to-day, and overall runs.
• Correlation was determined by analyzing 84 patient serum samples using both methods.

Main Results:

• The radiometric method exhibited higher coefficients of variation for within-run, day-to-day, and overall runs compared to RIA.
• A high coefficient of correlation (0.82) was observed between the radiometric assay and RIA for patient sera.
• Despite lower precision, the radiometric method demonstrated acceptable performance.

Conclusions:

• The radiometric assay is a viable alternative for gentamicin level determination, particularly in settings lacking RIA.
• While less precise than RIA, its correlation suggests clinical utility.
• Laboratories can consider the radiometric method when RIA is not accessible for gentamicin monitoring.