Step-by-step guide to performing a CLIA-compliant method comparison study, including sample requirements, statistical analysis, and acceptable bias thresholds.
Frequently Asked Questions
When is a method comparison study required?
When placing a new analyzer into service, adding a new reagent system for an existing test, or demonstrating two instruments running the same analyte produce equivalent results.
How many specimens does it need?
A minimum of 40 patient specimens spanning the full analytical measurement range, deliberately collected at low, mid, and high concentrations.
Why patient specimens instead of QC material?
Fresh patient samples reflect the actual matrix the methods encounter in routine testing; QC materials do not.
What statistics does it use?
Slope, y-intercept, Pearson correlation coefficient, and bias at medical decision points. Deming or Passing-Bablok regression is preferred over ordinary least squares because it accounts for error in both methods.
How do you set pass or fail?
The laboratory or manufacturer sets acceptable limits for slope, intercept, and bias, defined before running the study, with bias at decision points within total allowable error. CLSI EP09-A3 is the reference protocol.