Define (Method, Map, Formula and Curve) | 77
ELx800 Operator’s Manual
Positive / Negative Calls for Cutoff
After the greyzone is defined, calls for the sample wells (
POSitive, NEGative,
EQUIVocal) must be defined.
S A M P L E >
UT
0 5 % : P O S
P O S N E
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+(CUTOFF*GREYZONE)) and
SMP >= (CUTOFF-(CUTOFF*GREYZONE))
POS:
SMP > (CUTOFF+(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>CUTOFF+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
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