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Statistics - To little RNA or on detection limit

Statistics - To little RNA or on detection limit - Real-Time PCR and Quantitative PCR Forum

Statistics - To little RNA or on detection limit - Real-Time PCR and Quantitative PCR Forum


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Old 02-17-2009, 03:54 PM
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Default Statistics - To little RNA or on detection limit



How do I interpret qPCR result which are on the detection limit or were the amount of RNA is to low to detect? How should calculate the statistics on these and how should I present these values?

Thanx
//Olivia
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Old 02-17-2009, 04:14 PM
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Default Re: Statistics - To little RNA or on detection limit

You'll need to know what does it mean 'too low to detect' first.

Do you know what is the detection limit of your assay? If yes, then the values you present are < ZZZ (where 'ZZZ' is your detection limit), for X number of replicates in Y number of runs.

If the amount of your RNA is too low to detect you probably don't have much data to calculate any statistics. The question is what statistics do you want to calculate? And is your RNA concentration too low in all your runs or just in some (what's the percentage)?
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Old 02-17-2009, 04:27 PM
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Default Re: Statistics - To little RNA or on detection limit

I know my detection limit and that's a way to present my data, thanx.

I compare two groups: one healthy and one sick. In the healthy group the transcript level should be low, sometimes it is undetectable or on the detection limit (approx in 15%of the cases). Statistically I would like to separate these two groups, but to put the level to zero in the samples with undetectable RNA is not fair. Right?
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Old 02-17-2009, 05:16 PM
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Default Re: Statistics - To little RNA or on detection limit

You're right. The level in the healthy group can be presented as '≤detection limit' (because some samples, as you say, are on detection limit and some below).

I think you'll need to establish whether there is statistically significant difference between the values you get for sick and healthy groups, comparing the results for sick group with the result '≤detection limit' (with 95% confidence interval).
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detection , detection limit , limit , qpcr , rna , statistics


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