Discrepancies in Sigma Metrics Driven by Total Allowable Error Variability: Implications for QC Strategy and...

Area of Science:

• Clinical Biochemistry
• Laboratory Quality Management
• Analytical Performance Evaluation

Background:

• Sigma methodology is vital for assessing analytical performance and optimizing quality control (QC) in clinical labs.
• Inconsistent quality classifications arise from varying total allowable error (TEa) sources impacting sigma calculations.
• This study addresses the need for harmonized TEa selection to ensure reliable laboratory quality assessment.

Purpose of the Study:

• To evaluate the impact of different TEa guidelines on sigma metrics.
• To assess how TEa variations influence internal quality control (IQC) strategies.
• To highlight the necessity for harmonization in TEa selection for clinical laboratories.

Main Methods:

• A 3-month prospective observational study in a clinical biochemistry laboratory.
• Sigma metrics calculated for 14 analytes using internal and external QC data at two levels.
• Comparison of three TEa sources: CLIA 2025, RIQAS, and EFLM, with IQC adapted using Westgard rules.

Main Results:

• Significant variability in sigma metrics observed across different TEa guidelines.
• Analyte classifications varied from 'world-class' to 'unacceptable' depending on the TEa source.
• Electrolytes showed consistently poor performance, and discrepancies influenced IQC procedure selection.

Conclusions:

• The selected TEa guideline critically influences sigma metrics and IQC planning.
• Current inconsistencies necessitate standardized TEa criteria for clinical relevance and achievability.
• Harmonization of TEa criteria will enhance comparability, optimize resources, and support evidence-based quality management.