In the first part of this series, we investigated the use of the coefficient of determination—R2—to measure goodness-of-fit. Specifically, we showed that it is an inadequate tool: a low R2 does not always mean a poor model fit; a high R2 does not always mean a good model fit; and it doesn’t even measure the…
One of the most important concepts in bioassay is that of replication. Test samples are regularly replicated 2 or 3 times. Multiple response measurements at each dose will, in general, result in a better estimate of the precision of our result. As with all biological experiments, however, there is often quite a lot of variability…
One of the most important metrics when analysing bioassay data is goodness-of-fit — how well does a dataset fit a chosen model? In development, this question can help determine which model is appropriate for a dataset, while new data will have to meet a goodness-of-fit criteria to ensure it is adequately represented by the chosen…
This is the third blog responding to the software discussions at the BEBPA US 2022 conference. Blog One: formulae can be found here and Blog Two: Algorithms used can be found here. The key driver for these sessions was the experience that many have had of different software and different versions of the same software…
This is the second mini blog responding to the software discussions at the BEBPA US 2022 conference. Blog One: Formulae can be found here. The key driver for these sessions was the experience that many have had of different software and different versions of the same software giving different results. This causes problems with RP…
Myself, and my colleague Brooke, attended the BEBPA US virtual meeting last week and reported back on the presentation and round table discussions on relative potency software, including some questions about the use of different types of statistical model. The key driver for these sessions was the experience that many have had of different software…
Choosing the right Parallel Line Analysis (PLA) software for your lab is not an easy task. Whilst there are several packages available, and most can perform an adequate standard job, at least for development, it can be a challenge to know what aspects to consider. This is an important consideration as choosing the right software…
At the recent BEBPA meeting, in response to the question: ‘If you have a zero dose control on your plate do you include it in your 4PL model?’ 78% responded either “no” or “don’t know” or “did not know I could”. Well you can! Just add them into the datapoints for the reference and/or the…
Accuracy and Precision are properties of an experiment which are often conflated — not least because they are often synonymous in everyday conversation. In science, however, they have separate, well-defined meanings. Of course, this also applies to bioassay, so we thought we’d take a look at the difference here. Accuracy is the ability of an…
It has been sometime since I have set foot in a lab, but the thought of seeing outliers in my data still sends a shiver down my spine – don’t you just internally (or externally) groan when you see them in your assay results? Do you mask them and pretend they are not there, or…
We have all experienced the frustration (and sometimes utter dejection!) of performing a bioassay to what you thought was near perfection only to come back, analyse the data, and find out your assay has failed goodness-of-fit. This can happen even when, visually, the data points look to be very close to the fitted model! What…
Correlates of protection in determining vaccine efficacy is a topic of particular interest, given the current COVID-19 climate and the spotlight on vaccine development. Here at Quantics, we have a wealth of experience working with correlates of protection in vaccine development so we thought we would take a look back on our paper Estimating vaccine…
Bioassay simulation can be used during assay development maintenance to supplement and complement the information gained from lab experiments. Bioassay simulation assumes that the available real data is a representative sample of all the real data sets that might be created over the life of the assay. The mathematical properties of this sample can be…
Here, we investigate the difference between true replicates and pseudo-replicates, and discuss the problems that may arise if this difference is ignored or misunderstood in bioassay statistical analysis. Quality Control by sampling Consider a manufacturing process that makes widgets. To check the quality of a batch, a number of widgets randomly selected from the batch…
Software systems for calculating relative potencies and other bioanalytical results often provide a choice of variance estimation method, usually: Residuals, Lack of fit Error and Pure Error. This defines how the confidence limits on the reportable result are calculated. So which should you choose? The answer is simple. If the reportable result is calculated in…
Interpolation analysis is used to find the concentration of a substance in a sample. For biologics, this is often used in ELISA and other bioanalytic analyses. This blog introduces interpolation analysis for ELISA and presents a new method developed by Quantics. The Bursa-Yellowlees Method uses the available ELISA data more effectively and greatly simplifies the…
We previously discussed the purpose of system suitability tests and sample suitability tests and gave some examples of each. However, we did not explain how to actually set the limits for these tests: suitability criteria. In this blog we will discuss this and go through a couple of examples of how to set suitability criteria…
Suitability tests for bioassay are often confusing. In this blog, we discuss the two types of suitability tests: System suitability tests and Sample suitability tests. The blog is deliberately simplistic in approach to aid basic understanding. In practice, the use of the various System and Sample suitability criteria may be more complex. We’ll focus mainly…
LD50 assays and challenge assays both measure the time to an event, often death, for each animal. However the standard statistical approach to the analysis of the data treats the endpoint as binary – alive / dead – at a given point in time. This is inefficient use of the data. Here, we will recommend…
It often happens that the precision required from a relative potency (RP) bioassay cannot be achieved using a single plate. In this situation the usual approach is to repeat the assay two or more times1. Each run of the assay will give a separate relative potency result. These are then combined to give a single…