I performed ELISA in GraphPad Prism to calculate the concentrations of progesterone and cortisol metabolites in feces samples of deer. Unfortunately, the readings of concentrations that I get mostly negative. Anyone knows what is the best way for me to present the data even though it is in negative values? Any paper that you might suggest me to refer regarding this problems.
I am not sure I understand the problem, well.
Do you mean some samples had optical density of negative value?!
May you give the optical density of the standard and the negative sample?
If you are getting negative values, it means the signal was lower than the baseline of the standard curve.
If the negative value was small enough to be considered random variation around the baseline, then you should report the result as less than the lower limit of measurement (whatever the lowest measurable value is in the ELISA).
If the negative value was way below the baseline, then there is a problem with the assay. The sample may be causing some sort of interference.
Did your standard curve work? If you’re below the lowest value of the standard, then the value should be considered “Not detected, N.D.”
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