Cutoff, Report – Bio-Rad iMark Microplate Absorbance Reader User Manual

Page 17

iMark Microplate Absorbance Reader Instruction Manual

5. Cutoff

report

The Cutoff report provides a qualitative report of the relative magnitude of the absorbance values or converted
concentrations on the plate.

Four types of cutoff reports are supported; ranged constant, single constant, formula and ratio. These and their
subtypes are listed below.

a. Ranged Constant

The user inputs Positive and Negative values to be used as the cutoff.

For units designated "Abs", if the absorbance of a well is within the positive and negative cutoff values, the
well is scored "*". If the absorbance of a well is greater than the positive value, the well is scored "+", and if
the absorbance of a well is below the negative value, the well is scored "-".

For units not designated "Abs", the absorbance value of each well is converted to the concentration value
using the curve fit constants of the curve fit report. If the concentration of a well is within the positive and
negative cutoff values, the well is scored "*". If the concentration of a well is greater than the positive value,
the well is scored "+", and if the concentration of a well is below the negative value, the well is scored "-".

b. Single Constant

The user inputs Positive and Gray zone values to be used as the cutoff.

For units designated "Abs", if the absorbance of a well is within the gray zone value of the positive cutoff
value, the well is scored "*". If the absorbance of a well is more than the gray zone value and greater than the
positive value, the well is scored "+", and if the absorbance of a well is more than the gray zone value below
the positive value, the well is scored "-".

Upper cutoff absorbance = Positive absorbance + ((Gray zone/100) * Positive absorbance)

Lower cutoff absorbance = Positive absorbance – ((Gray zone/100) * Positive absorbance)

For units not designated "Abs", the absorbance value of each well is converted to the concentration value
using the curve fit constants of the curve fit report. If the concentration of a well is within the gray zone value
of the positive cutoff value, the well is scored "*". If the concentration of a well is more than the gray zone
value greater than the positive value, the well is scored "+", and if the concentration of a well is more than the
gray zone value below the positive value, the well is scored "-".

Upper cutoff conc. = Conc. of positive controls + ((Gray zone/100) * Conc. of positive controls)

Lower cutoff conc. = Conc. of positive controls - ((Gray zone/100) * Conc. of positive controls)

c. Formula

The mean absorbance values of the Positive and Negative wells defined in the plate map are used for the
cutoff formula calculation.

The 12 types of formula-based cutoff reports are:

k * CNx

vii.

k + CNx

ii.

k * CPx

viii.

k + CPx

iii.

k * COx

ix.

k + COx

iv.

CNx / k

k*CNx + CPx

CPx / k xi.

(CNx + CPx) / k

vi.

COx / k

xii.

k1*CNx + k2*CPx