Our experience with quality control in current growth hormone assays

Area of Science:

• Clinical Chemistry
• Endocrinology
• Laboratory Medicine

Background:

• The German Society for Clinical Chemistry conducts interlaboratory surveys for endocrine parameters, including human growth hormone (GH).
• GH testing lacks a universally accepted reference method, making 'true value' determination impossible.
• Surveys evaluate participant agreement using medians and percentiles, with 60-80 labs and 12-16 kits participating annually.

Purpose of the Study:

• To assess the variability and agreement of human growth hormone (GH) measurements across different laboratory methods and kits.
• To highlight discrepancies in GH testing, particularly at low concentrations relevant to pediatric endocrinology.
• To investigate the impact of method and kit changes on GH testing consistency.

Main Methods:

• Analysis of interlaboratory survey data for human growth hormone (GH) over several years.
• Calculation of medians and percentiles for all participants and subgroups using identical kits.
• Comparison of GH results across 12-16 different kits used by 60-80 participating laboratories.

Main Results:

• Participant results for GH exhibited considerable scatter, with variations up to several hundred percent.
• Discrepancies were most pronounced for specimens with low GH concentrations.
• While same-kit agreement was relatively good, different kits showed median variations as high as 250%.

Conclusions:

• Significant method-dependent variability exists in human growth hormone (GH) testing, necessitating kit-specific reference values.
• Frequent changes in GH testing methods and kits by laboratories and manufacturers may lead to discrepancies in patient results.
• Clinicians must be informed about potential discrepancies in GH parameters due to evolving testing methodologies.