Determination of Reference Intervals for Serum Total Calcium in the Vitamin D-Replete Pediatric Population
The Journal of Clinical Endocrinology & Metabolism November 11, 2013 jc.2013-3105
Jeffrey D. Roizen,
Michael A. Levine and
Dean C. Carlow
Division of Endocrinology and Diabetes (J.D.R., M.A.L.) and Division of Pathology and Laboratory Medicine (V.S., D.C.C.), The Children’s Hospital of Philadelphia, and University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104
Address all correspondence and requests for reprints to: Dr Dean Carlow, Division of Pathology and Lab Medicine, The Children’s Hospital of Philadelphia, 34th and Civic Center Boulevard, Philadelphia, Pennsylvania 19104. E-mail: dc8236710 at yahoo.com.
Context: Widespread vitamin D insufficiency raises concerns regarding the reliability of reference intervals for serum calcium.
Objective: We sought to determine the reference intervals for serum total calcium in pediatric subjects with normal [≥20 ng/mL (50 nmol/L)] serum 25-hydroxyvitamin D [25(OH)D].
Design and Participants: This was a retrospective study of laboratory data obtained from all patients at The Children’s Hospital of Philadelphia from July 1, 2011, through June 30, 2012. Patients in the renal unit, the endocrine unit, or a critical care unit were excluded. Total serum calcium was determined using a colorimetric assay and serum 25(OH)D was determined by liquid chromatography tandem mass spectrometry. We ascertained 4629 subjects who had a serum 25(OH)D between 20 and 80 ng/mL (50–200 nmol/L) and a serum calcium level determined within 30 days of the 25(OH)D measurement. For comparison, we used data from an unselected cohort of patients (n = 106ü220).
Results: Parametric analyses generated age-specific reference intervals for serum total calcium for each of several age groups (
- 0–90 d old,
- 91–180 d old,
- 181–365 d old,
- 1–3 y old,
- 4–11 y old, and
- 12–19 y old).
A two-way ANOVA with Tukey’s correction showed significant differences between the lower limits of normal (P < .001) and the normal range (P < .001) but not for the upper limit of normal for these subjects compared with unselected subjects.
Student’s t tests revealed significant differences at all ages between calcium concentrations in those with 25(OH)D values between
- 20 and 30 ng/mL and those with 25(OH)D values between
- 30 and 80 ng/mL.
Conclusions: These reference intervals refine previous normal ranges that likely included subjects with vitamin D deficiency.
Received August 10, 2013. Accepted October 15, 2013.
Copyright © 2013 by The Endocrine Society
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