LOD Cut Off Cycle

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LOD Cut Off Cycle

Postby ongwaik » Tue Mar 31, 2009 1:16 pm

For the LOD function, the cut off cycle is fixed to 33. What is the reason behind this? Under what circumstances should I change it? I noticed the plot will change substantially as I modify the cut off cycle. Does the plot have to be in a certain shape in order to be regarded as a good plot?

Eppendorf Asia Pacific
Posts: 11
Joined: Fri Feb 13, 2009 8:12 am

Re: LOD Cut Off Cycle

Postby Anders Bergkvist » Tue Mar 31, 2009 4:08 pm

The LOD feature in GenEx is based on digital detection in samples in a dilution series. Analyzing meltcurves may help you define an upper limit of quantification cycle of samples that you can detect. This is the value you should enter as the cut off cycle. The value 33 is simply the default, but you would need to adjust that to your own data set.

The LOD (in terms of concentration of analyte) is generally expressed as the amount of analyte at which the analytical method detects the presence of the analyte at least 95% of the time. This parameter is calculated in the GenEx feature.

Like you observe, the shape of the curve will depend on what you set for your cut off cycle. It can be different, although you would expect to have both positive and negative samples (the red dots) in your data set. If your cut off cycle is set so that all samples are either positive or negative the feature will not yield reasonable results.

Best wishes,
Anders Bergkvist
Posts: 31
Joined: Wed Jul 02, 2008 9:06 am

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