Scoring variability of micronuclei in binucleated human lymphocytes in a case-control study

Area of Science:

• Cytogenetics
• Biomonitoring
• Radiation Biology

Background:

• The micronucleus test in binucleated lymphocytes is a key assay for biomonitoring, mutagenicity, and radiosensitivity assessment.
• Inter-laboratory and inter-scorer variability can affect the reliability of micronucleus test results.
• International scoring criteria have been established to standardize the assay.

Purpose of the Study:

• To analyze scoring variability in the micronucleus test within a case-control study setting.
• To identify sources of variation impacting micronucleus frequency measurements.
• To assess the impact of scorer differences and experimental factors on assay reproducibility.

Main Methods:

• Analysis of variance (ANOVA) was used to assess variability in repeat measurements from blood donors.
• Coefficient of variation (CV) was calculated to quantify measurement variability.
• Normalization techniques were applied to account for biological and experimental variations.

Main Results:

• Blood sample storage time, donor characteristics (including disease status), and scorers were identified as significant sources of variation.
• Overall CV was 24.3%, reduced to 6.8% after normalization, indicating 'pure counting error'.
• Scorer-specific CVs ranged from 5.5% to 9.5%, with no clear link to experience; a general decline in micronuclei frequency was observed over time.

Conclusions:

• Significant scorer variability exists in the micronucleus test, impacting biomonitoring accuracy.
• Unrecognized changes in scoring criteria or other factors may contribute to observed temporal declines.
• Automated counting or the use of reference slides is recommended for long-term studies to enhance reproducibility.