Thread: Detection limit

Hi everyone,

I was wondering, how can I calculate the detection limit of a enumeration technique for microbiology?

Thank you in advance.

Originally Posted by PhDemon

Microbiology is not my area but I have experience of doing this for spectroscopic/analytical chemistry (GC-MS etc.) techniques. You will need to provide more information about the technique. Generally the detection limit is the point at which the "signal" is able to be separated from the "noise" i.e. the signal is a factor of "x" greater than standard deviation in signal changes due to random noise. For example a detection limit may be quoted as "50 ppm; S/N =3" meaning at a concentration of 50 ppm the signal is 3 times greater than the standard deviation in the signal due to noise.

I would like to know the detection limit of the enumeration technique Miles and Misra of 1938. I know I've to establish a lower and upper limits to make my counts and I did it: 15-150. But from here I don't know what math should I do.

Originally Posted by PhDemon

If your simply counting stuff I'm not sure of the best way of doing it sorry.

EDIT: This pdf may be useful especially bit on "Countable range on plate" section "Lower limit".

Thank you anyway for your help and the pdf