Bio-Tek ELx800, Operator'S Manual

Page: 107 / 214

Define (Method, Map, Formula and Curve)
|
79
Positive / Negative Calls for Cutoff
After the greyzone is defined, calls for the sample wells (
POS
itive,
NEG
ative,
EQUIV
ocal) must be defined.
S A M P L E > C U T O F F + 0 5 % : P O S
P O S N E G
Select
POS
or
NEG
to select the call that will be assigned to samples
greater than the cutoff value plus the greyzone.
If, for example,
POS
is selected as shown in the above screen, calls
will be assigned according to the following equations (
SMP
represents the sample wells):
EQUIV: SMP <= ((CUTOFF*GREYZONE))
and
SMP >= (CUTOFF-(CUTOFF*GREYZONE))
POS: SMP > ((CUTOFF*GREYZONE))
NEG: SMP < (CUTOFF-(CUTOFF*GREYZONE))
Examples
1. The cutoff between negative and positive calls should be calculated as the
average of the negative controls plus the OD value of 0.500. Samples
greater than the cutoff should be labeled as positive. No greyzone is
required.
•
For this example,
NC;x
(the mean of the NC wells) equals 1.000 OD
• The cutoff formula is
NC;x+0.5
•
The greyzone is
00%
•
POS
is selected for
SAMP>00%
• Calls are assigned to sample wells as follows:
EQUIV
if the sample equals 1.500
POS
if the sample is greater than 1.500
NEG
if the sample is less than 1.500
ELx800 Operator’s Manual