Biotek ELx808, Operator'S Manual, Page: 82 / 172

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| Chapter 3: Operation
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:
¾
EQUIV if the sample equals 1.500
¾
POS if the sample is greater than 1.500
¾ NEG if the sample is less than 1.500
2:
For a quantitative assay, samples with OD values greater than the STD2 mean
plus a 10% greyzone should be labeled as positive; samples with OD values less
than the STD2 mean minus the 10% greyzone should be labeled as negative. All
other samples should be considered equivocal.
• For this example, STD2;x (the mean of the STD2 wells) equals 2.000 OD
•
The cutoff formula is simply
STD2;x
•
The greyzone is
10%
•
POS is selected for
SAMP>10%
• Calls are assigned to sample wells as follows:
¾
EQUIV if the sample is greater than or equal to 1.800 and
less than or equal to 2.200
¾
POS if the sample is greater than 2.200
¾
NEG if the sample is less than 1.800
BioTek Instruments, Inc.