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Related Experiment Videos

Multi-factor designs. II. A design for identifying instruments with sample-to-sample carryover and drift.

B Schlain1, J S Krouwer

  • 1Ciba Corning Diagnostics Corp., Medfield, MA 02052.

Clinical Chemistry
|October 1, 1989
PubMed
Summary

This study introduces a new assay design to detect subtle systematic errors like sample carryover and drift. This method is crucial for accurate measurements of analytes near zero, as demonstrated with thyrotropin measurements.

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Area of Science:

  • Clinical Chemistry
  • Analytical Chemistry
  • Biomedical Assay Development

Background:

  • Accurate quantification of analytes is critical in clinical diagnostics, especially for those with decision points near zero.
  • Systematic errors, such as analyte drift and sample-to-sample carryover, can significantly impact assay accuracy.
  • Existing methods may not adequately address the simultaneous estimation of low-level drift and carryover.

Purpose of the Study:

  • To present a novel, nearly orthogonal two-level experimental design for simultaneously estimating drift and sample-to-sample carryover.
  • To demonstrate the utility of a weighted analysis approach within this design.
  • To highlight the importance of detecting these systematic errors in high-range analyte assays with low medical decision points.

Main Methods:

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  • Implementation of a nearly orthogonal two-level experimental design.
  • Application of a weighted analysis technique to estimate drift and carryover.
  • Validation using a specific assay for thyrotropin (TSH).

Main Results:

  • The proposed design successfully estimated both drift and carryover simultaneously.
  • A low level of sample-to-sample carryover (0.08%) was detected.
  • Concentration-dependent negative drift was observed in the thyrotropin assay.
  • The method proved effective even with a small number of samples (32) in a single run.

Conclusions:

  • The described two-level design with weighted analysis provides a robust method for identifying and quantifying low-level systematic errors in bioassays.
  • This approach is particularly valuable for assays where accuracy near zero is critical, such as for thyrotropin.
  • The findings underscore the need for careful assay design to mitigate the impact of drift and carryover on clinical results.