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How to calculate LOD of elisa


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5 replies to this topic

#1 profenpaul

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Posted 18 November 2014 - 12:51 PM

Commercial elisa kit was used to measure IgA in pig saliva. Now how can I calculate Absorbance LOD and concentration LOD from my results. The calibration curve is 4 parametric. In additon, mean OD at zero calibrator is 0.06 and SD 0.0045. Thank you in advance for your valuable suggestions.



#2 tkf

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Posted 24 November 2014 - 08:02 AM

Generally, the LOD OD = (mean OD at zero calibrator) + 3 x SD.

 

The LOD concentration can be calculated from the 4PL curve by plugging in the LOD OD calculated above.

 

Best,

tkf



#3 paul73

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Posted 25 November 2014 - 12:38 PM

Hi tkf, thanks a lot for your valuable suggestion. I calculated LOD OD =0.0735. But my 4PL curve intercepted y axis at 0.385 OD. How can I compare my calculated LOD OD with standard curve to get the conc. from x axis. Thank you in advance for your valuable suggestions.

#4 tkf

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Posted 26 November 2014 - 05:26 AM

It seems your standard curve range is broad, which can result in a high y-intercept. You can either fix bottom asymptote value to the background value or rerun the std curve in a narrower range to get a better fit in the low concentration range.



#5 paul73

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Posted 26 November 2014 - 10:31 AM

I ran the test 4 times but resulted same. Moreover accuracy and precision was in acceptable range for the sample. U right i should do fix bottom asymptote value with my background. But u dont know how can i do this. Can u please tell me about this

#6 tkf

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Posted 26 November 2014 - 03:04 PM

I meant you should try running a different std curve with lower concentration values.

As far as changing the bottom asymptote value, it depends what software you are using.






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