[R] Fitting ELISA measurements

[Allen Liu]

Christopher Anderson <recsa <at> channing.harvard.edu> writes:

> 
> Hello,
> 
> I am trying to fit my Elisa results (absorbance readings)  to a standard
> curve. To create the standard curve model, I performed a 4-parameter
> logistic fit using the 'drc' package (ExpectedConc~Absorbance). This gave me
> the following:
> > FourP
> 
> A 'drc' model.
> 
> Call:
> drm(formula = Response ~ Expected, data = SC, fct = LL.4())
> 
> Coefficients:
> b:(Intercept)  c:(Intercept)  d:(Intercept)  e:(Intercept)
>         1.336          6.236         85.521         59.598
> 
> > summary(FourP)
> 
> Model fitted: Log-logistic (ED50 as parameter) (4 parms)
> 
> Parameter estimates:
> 
>               Estimate Std. Error  t-value p-value
> b:(Intercept)  1.33596    0.15861  8.42309  0.0011
> c:(Intercept)  6.23557    3.18629  1.95700  0.1220
> d:(Intercept) 85.52140    2.15565 39.67313  0.0000
> e:(Intercept) 59.59835    5.18781 11.48815  0.0003
> 
> Residual standard error:
> 
>  1.866876 (4 degrees of freedom)
> 
> Now that I have the 4 parameters, how do I fit the absorbance readings for
> the analytical unknowns to the standard curve model (as to estimate the
> concentrations of my unknown analytical samples)?
> I can use the argument 'predict', but this predicts absorbance given
> concentrations (y given x), I need to predict concentrations give absorbance
> (x given y).
> 
> Thanks!
> Chris
> 
> 	[[alternative HTML version deleted]]
> 
> 

Hi Chris,

Disclaimer: I am a technical support supervisor for Hitachi Solutions.

I have a solution that does not involve using R but rather a software package 
that is dedicated to ELISA analysis with focus on the 4PL and 5PL model 
equations.  If you are not interested, then please disregard the rest of this 
message.

MasterPlex ReaderFit is a software package dedicated to the quantitative 
analysis of ELISA data.  Once you fit your standards, all concentrations of your 
unknown samples will automatically be interpolated or extrapolated.  

Here is a link to a free 14-day trial of the software that is fully-functional:

http://www.miraibio.com/masterplex-readerfit/curve-fitting-for-plate-
readers.html

If you would like, I can assist you with the analysis of your data.  You can 
email me at aliu at miraibio dot com and I would more than happy to do some data 
analysis with you.

In addition, here is a blog post that I have written a while back for some tips 
on ELISA data analysis:

http://www.miraibio.com/blog/2009/06/tips-for-data-analysis/

I hope this helps.


Best Regards,

Allen Liu