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StatLIA® measures relative potency and parallelism even for bioassays that yield difficult, ill-behaved data.

StatLIA® Parallelism measures the biological similarity between two molecules quantitatively, where parallelism and non-parallelism can be directly compared. StatLIA® Parallelism using chi symbol methodology provides results that are:

Good and Bad Assays
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  • Consistent
    Determine potency even for assays with high variation using StatLIA’s correct weighting
5P Logistic
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  • Accurate
    Improve the accuracy of full curve parallelism analysis with StatLIA’s TrueFit™ 5PL

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  • Reliable
    Measure parallelism and nonparallelism directly, accurately, every time using chi symbol method

Presentations and Posters

U.S. Pharmacopeia Bioassay Workshop, August 2008
Download Brendan CTO Presentation: "Nonlinear Systems: A Comparison of Approaches to Similarity Testing."
Link to all Presentations at USP Bioassay Workshop.

IBC Biological Assay Development & Validation Conference, May 2008
Download MERCK Presentation:
(MERCK Uses STATLIA Parallelism Metric to Set Acceptance Criteria)
Download Presentation: "Comparison of Methods Used to Measure Parallelism"
Download Poster: "Comparison of Methods Used to Measure Parallelism"
Data: (Request Data Used In Parallelism Comparison Study)


Measuring Parallelism, Linearity and Relative Potency in Bioassay and Immunoassay Data, Gottschalk PG, Dunn JR, Journal of Biopharmaceutical Statistics, 2005; 3:437-463.  (Free Reprint Available)


Key Parallelism Metrics

  • chi symbol Probability: Probability the two curves are parallel based on the Chi-Square statistic
  • chi symbol  Statistic: Direct measure of the amount of nonparallelism between two curves
  • Relative Potency: Relative potency between the two curves
  • Low Confidence Limit: Lower 95% confidence limit for the relative potency
  • High Confidence Limit: Upper 95% confidence limit for the relative potency
  • Confidence Limit Ratio: Ratio of the logs of the upper and lower confidence limits
  • IC25, IC50, IC75: Percent concentration of the maximum response calculated from the unknown dilution curve
  • Dil25, Dil50, Dil75: Equivalent dilution factor of the inhibitory concentration, e.g. (Dil*Conc)/IC50
  • Fit Probability: Measurement of how well the computed curve fit the observed data points
  • Limits of Quantitation and Detection: Limits of Quantitation and Detection based on the observed data points
  • Dilution CV's: Coefficient of variation of all reportable concentrations in a dilution series
  • Download Parallelism Poster PDF File
  • Download Parallelism PDF File

Full Logistic Curve Parallelism Method

  • Use a powerful weighted 5 parameter or 4 parameter logistic model to fit the curves
  • Measure the reliability of the standard curve
  • Measure the reliability of the unknown dilution curve
  • Measure the parallelism between the two curves using the chi symbol Statistic and chi symbolProbability
  • Download Parallelism Fact Sheet PDF file

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