Rethinking repeat testing: when analytical criteria tell different stories

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Medical Diagnostics

Background:

• Repeat testing is frequent in emergency clinical chemistry.
• Its clinical necessity is often uncertain, leading to potential delays and resource waste.

Purpose of the Study:

• To evaluate the necessity of repeat testing using three analytical criteria: laboratory-specific observed total allowable error (TEa_Obs), CLIA-based TEa (TEa_CLIA), and reference change values (RCV).

Main Methods:

• A retrospective analysis of 18,736 repeat result pairs across 23 analytes was performed.
• Each pair was classified as necessary or unnecessary based on TEa_Obs, TEa_CLIA, and RCV.
• Agreement between criteria was assessed using Cohen's kappa (κ), and turnaround time (TAT) for necessary vs. unnecessary repeats was compared.

Main Results:

• TEa_Obs deemed 86.2% of repeats unnecessary, TEa_CLIA 93.7%, and RCV 96.7%.
• Agreement between criteria was generally low to moderate (κ <0.2 to >0.8).
• Necessary repeats were associated with longer turnaround times, with varying statistical significance.

Conclusions:

• The choice of analytical criterion significantly impacts the interpretation of repeat testing necessity and operational outcomes.
• Implementing rule-driven workflows combining TEa_Obs, TEa_CLIA, and RCV in laboratory information systems (LIS) can reduce unnecessary repeats, stabilize TAT, and optimize resource use without compromising patient safety.