Comments(1)

Delta Ct miscalculation?

Bruno Maranda   (24 February 2006)  Hopital Ste-Justine

To the editor:

It was with great pleasure that I read this article. Working also on quantitative real-time PCR I attempted to use their formula with my own data. The authors present their calculations for corrected Ct in great details. However, I do not obtain the same fold change results. PCR doubles the amount of DNA at each cycle if amplification efficiency is near 100%. If we observe a difference of one Ct (-1) it represents half of the reference amount of DNA and not simply a loss of one copy. In their case, it represents a microdeletion. If you observe a positive difference of one Ct (+1), this represent twice the amount of refence DNA. In their case it would be 4 copies of the genes in the 22q11.2 region and not three copies as the authors suggest. I have not found any patient with trisomy 22 as reported in reference 25, but one patient with 4 copies of 22q11.2 region. I wonder if this is the patient that they have used to study gain of copies. I would like to get further information about their calculations and the patient with gain of copy(ies).

Competing interests

None declared

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