Standardization of gamma-glutamyltransferase assays by intermethod calibration. Effect on determining common...

Area of Science:

• Clinical Chemistry
• Biochemical Assays
• Laboratory Medicine

Background:

• Assessing consistency of gamma-glutamyltransferase (GGT) activity results across different assays.
• Evaluating harmonization of GGT assays through common calibration material.
• Determining if harmonization can establish common reference limits for routine GGT methods.

Purpose of the Study:

• To estimate the improvement in GGT activity result consistency after calibration.
• To evaluate if harmonization leads to common reference limits for routine GGT methods.
• To assess the impact of a common calibrator on GGT assay comparability.

Main Methods:

• Seven laboratories measured GGT activity using routine systems, with and without a common multi-enzyme calibrator (IFCC value).
• All samples were re-measured using the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference procedure.
• Healthy subjects and subjects with elevated GGT were analyzed.

Main Results:

• Common calibration significantly reduced differences in GGT means between routine methods and the IFCC procedure.
• After calibration, only one laboratory showed a significant difference from the IFCC procedure.
• Common reference limits (11-49 U/L) were calculated for calibrated methods, showing good agreement with IFCC values.

Conclusions:

• Common calibration enhances consistency among routine GGT assays.
• This approach allows for the definition of common reference limits similar to IFCC recommendations.
• Harmonization offers benefits for GGT-related prevention, screening, diagnosis, monitoring, and epidemiological studies.