We really appreciate the comments from Drs. Reibnegger and Fuchs regarding our recent publication "Normalization of urinary pteridines by urine specific gravity for early cancer detection [Clin. Chim. Acta 435 (2014) 42-47]". In their letter, Drs. Reibnegger and Fuchs identify several potential concerns regarding our recent publication [1] that evaluated the normalization performance of urine specific gravity (USG) and urinary creatinine with respect to the diagnostic properties of selected pteridines in discerning aggressive and benign breast cancers. Their letter not only provides unique insights that are both relevant and helpful to many researchers engaging in similar studies, but also provides a wonderful opportunity for us to address these potential concerns that may also be shared by other readers. We addressed all of the comments by Drs. Reibnegger and Fuchs in this letter.