We read with interest Dr. Cantinotti’s letter, in which he raises important issues pertaining to the challenges of performing and interpreting pediatric quantitative echocardiography. We agree that many sources of error cannot be eliminated by parametric normalization. Loading conditions, transitional physiology, agitation, and heart rate are only few of the confounding factors that influence the various measurements echocardiographers obtain every day.

That said, somatic growth is likely one of the most powerful confounding factors in quantitative echocardiography. Although the use of Z scores helps reduce this cofounding effect, new biases may be introduced if proper statistical testing and control are not performed. Careful evaluation of residual biases in any newly proposed reference value is of paramount importance, but we showed that this has been inconsistently reported. Our work was complementary to Cantinotti et al. ‘s study in which they underlined the paucity of reference values based on standardized approaches and derived from large cohorts of healthy children.

Both Cantinotti et al. ‘s report and ours emphasize that much remains to be done to obtain reliable reference values for two-dimensional echocardiographic measurements. This is also especially true for reference values of functional echocardiographic parameters, for which loading conditions and heart rate are often powerful confounders. Appropriately acquired data following accepted guidelines and adequately normalized values will ease our interpretation of the wealth of data acquired during echocardiographic studies. But above all, clinical judgment and good knowledge of the specificity of a patient’s condition and hemodynamics must prevail.