Estimation of the uncertainty of analyte concentration from the measurement uncertainty

Abstract

Ligand-binding assays, such as immunoassays, are usually analysed using standard curves based on the four-parameter and five-parameter logistic models. An estimate of the uncertainty of an analyte concentration obtained from such curves is needed for confidence intervals or precision profiles. Using a numerical simulation approach, it is shown that the uncertainty of the analyte concentration estimate becomes significant at the extremes of the concentration range and that this is affected significantly by the steepness of the standard curve. We also provide expressions for the coefficient of variation of the analyte concentration estimate from which confidence intervals and the precision profile can be obtained. Using three examples, we show that the expressions perform well.

Key Words::

• Analytical chemistry methods
• clinical chemistry tests
• immunoassay
• logistic models
• uncertainty

Declaration of interest: The authors report no conflicts of interest when this study was being carried out. The authors alone are responsible for the content and writing of the paper. Dr Cooke now works for a small company that develops immunoassay systems.