Bio-Rad Model 550, Ultramark, and Benchmark Microplate Reader Accessories - Manual (Page 10)

Notes:
1. If an out-of-range absorbance is measured in one of the blank wells,
then the report will show:
Blank mean *.***
Std. Dev. *.***
If the out-of-range value is below -3.500, then the asterisks will be
preceded by a negative sign (-).
2. If the number of blanks is zero, then the report will show:
Blank mean 0.000
Std. Dev. 0.000
3. If the number of blanks is one, the report will show:
Blank mean Raw absorbance value of the one blank well
Std. Dev. 0.000
C. The MATRIX REPORT provides a qualitative report of the relative magnitude of
the absorbances on the plate. The absorbance range defined by the upper and lower
limits (set as described in Section 4.3, Set Limit Mode) is divided into 10 equal par-
titions, numbered 0 through 9. The blank-subtracted absorbance value of each well is
classified according to the partition of the matrix to which it corresponds, and is
reported as a single digit. Wells with absorbances greater then the upper limit are rep-
resented by plus signs (+), and wells with absorbances less then the lower limit by
minus signs (-).
D. The LIMIT REPORT provides a qualitative YES/NO report. Wells with blank-
subtracted absorbances between the upper and lower limits are represented with an
asterisk (*), wells with absorbances below the lower limit by minus signs (-), and
wells with absorbances greater then the upper limit by positive signs (+).
E. The CUTOFF REPORT provides a qualitative score for each well compared to a
cutoff value. If the absorbance of a well is within 10% (i.e., +/-10%) of the cutoff
value, the well is scored ‘+/-’. If the absorbance of a well is more than 10% greater
than the cutoff value, the well is scored ‘+’, and if the absorbance of a well is more
than 10% below the cutoff value, the well is scored ‘-’.
The cutoff value may be assigned by either the CONSTANT method or the FOR-
MULA method. In the constant method, the user inputs an absorbance value to be used
as the cutoff, e.g. 1.000 O.D. By this example, all wells with absorbances between 0.9
and 1.1 will be scored ‘+/-’, all wells below 0.900 will be scored ‘-’ and all wells
above 1.100 will be scored ‘+’.
When the formula method is chosen, the user prepares both posititve and negative
controls. As many as eight sets of controls may be chosen. The mean absorbances
and standard deviations are calculated and reported for both sets of controls, and
then a cutoff value is calculated by the formula:
Cutoff value = Mean of negative controls + 0.10 * Mean of the positive controls
Consider an example in which the mean absorbance of the negative controls is 0.200
and the mean absorbance of the positive controls is 1.000. The calculated cutoff
value will be 0.300 (cutoff = 0.200 + 0.10 * 1.000) and wells with absorbances
between 0.270 and 0.330 will be scored ‘+/-’, wells with absorbances less than 0.270
or greater than 0.330 will be scored ‘-’ or ‘+’, respectively.
7