We thank Hofmann and colleagues (1) for their report corroborating our discovery that the method used to extract DNA from blood cells influences the measurement of telomere length (2). Hoffman and colleagues found that peripheral leukocyte telomere lengths measured by quantitative PCR were significantly longer in DNA that had been extracted by the ReliaPrep magnetic bead capture chemistry than in DNA extracted by the QIAamp column method. This echoes our finding that QIAamp DNA extraction yielded shorter telomeres than DNA extracted by either liquid phase phenol/chloroform or the salting out method Puregene. In addition, Hofmann and colleagues determined that QIAamp extracted samples had a higher copy number of mitochondrial (mt)DNA than mtDNA extracted by ReliaPrep. We acknowledge their important contribution highlighting that DNA extraction method may affect our ability to compare results across studies of not only telomere length but also with regard to mtDNA copy number.
These new results underscore our conclusion that the use of QIAamp extracted DNA for telomere length quantification is subject to systematic measurement error that may limit studies in detecting associations between telomere length and outcomes.
See the original Letter to the Editor, p. 1129
Disclosure of Potential Conflicts of Interest
No potential conflicts of interest were disclosed.