Inter-laboratory comparison of plasma catecholamine determinations using several different assays.

Area of Science:

• Clinical Chemistry
• Analytical Chemistry
• Biomedical Analysis

Background:

• Accurate measurement of plasma catecholamines (adrenaline, noradrenaline, dopamine) is vital for understanding physiological and pathological states.
• Existing analytical methods for plasma catecholamines exhibit variability, necessitating a comprehensive evaluation.

Purpose of the Study:

• To assess the inter-laboratory and inter-method variability of plasma catecholamine assays.
• To compare the performance of various analytical techniques, including radioenzymatic and high-performance liquid chromatography (HPLC) assays.

Main Methods:

• Thirty-four laboratories performed plasma catecholamine assays on four samples using diverse methods.
• Techniques included radioenzymatic assays, HPLC with electrochemical detection, and fluorimetric assays.
• Assays measured adrenaline, noradrenaline, and dopamine levels in basal and post-exercise plasma pools, as well as recovery of spiked analytes.

Main Results:

• Reasonable agreement on basal and post-exercise levels for adrenaline and noradrenaline, but considerable variability between methods and laboratories was observed.
• Fluorimetric assays yielded unacceptable results; radioenzymatic and reverse-phase HPLC methods showed high variability.
• Microparticulate cation exchange HPLC demonstrated the least variability, while reproducibility issues were noted for noradrenaline.
• Recovery experiments indicated a frequent need for improved precision in plasma catecholamine measurements.

Conclusions:

• Plasma catecholamine assays require enhanced standardization and continuous quality control to improve accuracy and reproducibility.
• Validation of new and modification of existing assays are critical areas for development.
• Specific HPLC methods, particularly microparticulate cation exchange, show promise for more reliable measurements.