Bioassay

In the most basic sense, relative potency bioassays consist of a comparison of the behaviour of a reference standard to that of a test sample. That process is not the topic of discussion here (we’ve covered it extensively elsewhere, in Potency Assay: Relative or Absolute, for example). What we want to examine is one of…

Picture the scene. You’re busily developing your assay and its data fits your chosen 4PL model beautifully. You’re just about to move onto validation—everything’s going so well!—but, out of an abundance of caution, you decide to re-run some of your data through a different software package. Disaster! It gives a different answer! Has something gone…

Relative. Thanks for reading…But wait a moment! Have you ever stopped to ask why relative potency (RP) assays are the most common potency assay? Perhaps there are cases where absolute potency (AP) would be better? Indeed, Quantics occasionally come across clients who continue to use AP for their assays. Are they incorrect? Potency is, put…

What are the most important properties of a new drug? Ultimately, we want to ensure that any new therapy treats what it is designed to treat—that it’s effective—and that the patient suffers as few negative consequences as possible while doing it—that it’s safe. These two criteria often boil down to what the drug does to…

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…

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…

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…

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…