EDTA analysis on the Roche MODULAR analyser

Area of Science:

• Clinical Chemistry
• Analytical Chemistry
• Biochemistry

Background:

• Patient specimens are susceptible to contamination from liquid-based, potassium-containing EDTA anticoagulant.
• Such contamination can lead to misinterpretation of laboratory test results.
• A need exists for a rapid method to detect EDTA contamination.

Purpose of the Study:

• To develop and validate a rapid, automated colorimetric assay for detecting EDTA contamination in patient specimens.
• To assess the accuracy and precision of the developed EDTA assay.
• To compare the new assay with an existing adjusted calcium difference measurement method.

Main Methods:

• An in-house EDTA assay was developed on the Roche MODULAR analyser.
• The assay's accuracy and precision were evaluated against an adjusted calcium difference measurement.
• Statistical analysis included slope, intercept, and correlation coefficient (r) calculations.

Main Results:

• The automated EDTA assay demonstrated good agreement with the adjusted calcium difference method (r=0.914).
• The automated method exhibited superior inter-assay precision (CV 3.4%) compared to the calcium difference method (CV 24.8%).
• Unequivocal EDTA contamination was detected at concentrations >= 0.2 mmol/L, with minimal interference from common confounding factors.

Conclusions:

• The described automated colorimetric assay is an accurate and precise tool for detecting EDTA contamination.
• The assay is rapid, providing results in just 3 minutes.
• This method is suitable for identifying EDTA contamination in unhaemolysed biochemistry specimens.