Long-term stability of laboratory tests and practical implications for quality management

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Analytical Performance Monitoring

Background:

• Adequate patient management relies on the long-term stability of analytical performance.
• Investigated patient data for documenting test stability and its impact on surrogate medical outcomes.
• Utilized multiyear patient and internal quality control (IQC) data for chronic kidney and thyroid disease monitoring.

Purpose of the Study:

• To assess the utility of patient data in documenting long-term analytical test stability.
• To evaluate the clinical relevance of observed analytical instabilities on patient outcomes.
• To compare patient data trends with internal quality control (IQC) data.

Main Methods:

• Plotted moving means of 50th percentiles from stratified patient data and daily IQC means.
• Assessed analytical instabilities against quality goals derived from biological variation.
• Investigated the effect of instabilities on result classification relative to reference intervals.

Main Results:

• Patient and IQC data generally showed good agreement, with deviations linked to non-analytical variation sources.
• Analytical instabilities primarily stemmed from reagent/calibrator lot changes and, for immunoassays, within-lot variations requiring frequent recalibration.
• The impact of biased results on medical decisions varied from negligible to significant, highlighting the need for performance assessment relative to biological variation goals.

Conclusions:

• Patient percentiles show significant potential for medium- to long-term analytical test stability assessment under specific conditions.
• Variations in analytical quality between different assays can substantially influence medical outcomes.
• Monitoring analytical performance using patient data is essential for ensuring reliable diagnostic accuracy and patient care.