Language:
English
In:
Clinical Chemistry, 02/01/2014, Vol.60(2), pp.424-424
Description:
We appreciate the interest in our recently published CALIPER (Canadian Laboratory Initiative for Pediatric Reference Intervals)1 manuscripts and are delighted to see that the publications are stimulating further discussion in the field. Overall, the authors of these letters have raised several important questions, but they appear to have overlooked some important points when reviewing the published studies. They also fail to acknowledge the numerous limitations inherent in interpretation of cortisol as addressed in our published articles: namely, that circadian rhythms in infants differ from those of adults, that the stress of phlebotomy can alter cortisol concentrations, and that we examined a single time point in each individual within a large population of children rather than multiple time points in a small number of individuals. That being said, in our population, the reference intervals did not differ significantly between morning and afternoon. We did not seek to answer in our studies whether the influence of circadian rhythms could be observed within individuals, but rather, whether such a change could be observed across the population. Of course, our population is ethnically diverse and is representative of a healthy population in Ontario, Canada. Therefore, we believe that our conclusions are not altered by points raised in these letters. We agree that performing sequential sampling for cortisol measurement at multiple time points over 3–5 days would be ideal to assess the diurnal variation for cortisol. However, such a determination was well beyond the scope of the recently published CALIPER studies, which established reference value distributions in a large, healthy population of children. We would like to respond first to the question raised by Rovnaghi et al. (1) regarding the differences in age partitions between the CALIPER immunoassay study published in Clinical Chemistry (2) and the HPLC-MS/MS study published in Clinical Biochemistry (3 …
Keywords:
Medicine;
ISSN:
0009-9147
E-ISSN:
1530-8561
DOI:
10.1373/clinchem.2013.218115
