I have measured Irisin levels in plasma and now I'm trying to analyze the results. As far as I have read, I need to perform a 4 parameter logistic regression, should I use logarithm for absorbances and for concentrations?
I use the program Prism GraphPad for that. The data used is only the concentration level of the standard curve and the optical density levels. Then I interpolate the values for the estimation of the concentration of the protein in my samples. After selecting the interpolate option, a parameters window is open, where I select the 4 parameter logistic regression.
I hope this can help you.
Did you apply logarithm in any moment to absorbances or the elisa concentrations?
Joana Antonela Asensio In Prism I had the interpolation with the logarithm applied to the standard curve already.
Hi Joana,
We recommend the use of a software that can generate a four-parameter logistic (4-PL) curve. If your plate reader didn't come with that kind of software, then you could use CurveExpert - a comprehensive curve fitting system for Windows. It is simple to use and you can obtain a model for your data quickly and easily. Please download a copy here:
https://www.curveexpert.net/download/
For data analysis of a competitive ELISA kit, we usually calculate the log of the concentration of the standard curve and then make a standard curve with log (concentration) as Y-axis, and O.D. value as X-axis by using regression and quadratic formula.
When we get the formula, we will put the O.D. of the sample in as X, and then calculate the y value. Finally, the concentration of the sample could be calculated as 10^y. We chose this method because it is easy to calculate. Some customers do not have special software to fit the standard curve. In this way, customers can fit the standard curve with Excel.
You could also use standard concentration as the X-axis and O.D. values as the Y-axis. Since the program calculates the sample concentration for you directly, there is no need to invert the concentration and O.D. If you still want to flip both the concentration and the absorbance, you can adjust the program settings or the data entryway.
I would suggest reaching out to the customer support of the ELISA kit supplier. I bet they will be happy to help you out.
I hope this helps.
Best regards,
Biomatik Team
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