Evaluation of three gentamicin serum assay techniques

Area of Science:

• Clinical Chemistry
• Pharmacokinetics
• Analytical Toxicology

Background:

• Accurate measurement of serum aminoglycoside concentrations is crucial for optimizing patient dosing and minimizing toxicity.
• Existing methods for therapeutic drug monitoring (TDM) of aminoglycosides include radioimmunoassay (RIA), enzyme-modified immunoassay (EMIT), and radiometric assays.

Purpose of the Study:

• To compare the performance of Syva--EMIT, New England Nuclear--RIA, and Johnston--BACTEC assays for determining serum aminoglycoside concentrations.
• To identify the optimal assay for use in a clinical aminoglycoside dosing service.

Main Methods:

• Serum samples were analyzed using EMIT, RIA, and BACTEC assay methods.
• Linear regression analysis was employed to compare the results obtained from the three assay techniques.
• Correlation coefficients (r²) and regression slopes were calculated to assess assay agreement.

Main Results:

• Significant positive correlations were observed between all three assay methods (p < 0.005).
• EMIT and RIA showed a highly significant relationship (p < 0.0005, r² = 0.90).
• EMIT was found to be the easiest and most accurate method for serum gentamicin determination; BACTEC was deemed unacceptable for clinical use.

Conclusions:

• The enzyme-modified immunoassay (EMIT) is the preferred method for routine clinical monitoring of serum gentamicin concentrations due to its accuracy and ease of use.
• Variations in BACTEC assay results may be linked to alterations in control serum pH.
• RIA and EMIT demonstrate strong agreement, supporting their reliability in therapeutic drug monitoring.