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Related Concept Videos

Essential Minerals for Bone Health01:31

Essential Minerals for Bone Health

The minerals contained in all of the food we consume are essential for our organ systems. However, certain essential minerals, such as calcium, phosphorus, magnesium, manganese, and fluoride, largely affect bone health.
Calcium and Phosphorus
Calcium is a critical component of bones, especially in the form of calcium phosphate and calcium carbonate. Since the body cannot make calcium, it must be obtained from the diet. However, calcium cannot be absorbed from the small intestine without...
z Scores and Area Under the Curve01:17

z Scores and Area Under the Curve

z scores are the standardized values obtained after converting a normal distribution into a standard normal distribution. A z score is measured in units of the standard deviation. The z score tells you how many standard deviations the value x is above (to the right of) or below (to the left of) the mean, μ. Values of x that are larger than the mean have positive z scores, and values of x that are smaller than the mean have negative z scores. If x equals the mean, then x has a z score of zero.
Bone Disorders01:29

Bone Disorders

Aging and its effect on bone remodeling is the most common cause of bone disorders. In young and healthy people, bone deposition and resorption happen at an equal rate to maintain optimal bone health.
Bone deposition is also affected by the levels of sex hormones like estrogen and testosterone that promote osteoblast activity and bone matrix synthesis. When the level of these hormones decreases due to aging, it causes a reduction in bone deposition. As a result, bone resorption by osteoclasts...
Introduction to z Scores01:05

Introduction to z Scores

A z score (or standardized value) is measured in units of the standard deviation. It indicates how many standard deviations the value x is above (to the right of) or below (to the left of) the mean, μ. Values of x that are larger than the mean have positive z scores, and values of x that are smaller than the mean have negative z scores. If x equals the mean, then x has a zero z score. It is important to note that the mean of the z scores is zero, and the standard deviation is one.
z scores help...
Introduction to z Scores01:06

Introduction to z Scores

A z score (or standardized value) is measured in units of the standard deviation. It tells you how many standard deviations the value x is above (to the right of) or below (to the left of) the mean, μ. Values of x that are larger than the mean have positive z scores, and values of x that are smaller than the mean have negative z scores. If x equals the mean, then x has a zero z score. It is important to note that the mean of the z scores is zero, and the standard deviation is one.
z scores help...
Bone Remodeling01:40

Bone Remodeling

Bone remodeling is a continuous and balanced process of bone resorption by osteoclasts and bone formation by osteoblasts. In adults, it helps maintain bone mass and calcium homeostasis. While mechanical stress can stimulate turnover as part of the normal maintenance and reparative process, several hormones also regulate bone remodeling.

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Related Experiment Video

Updated: Jun 10, 2026

Scanning Skeletal Remains for Bone Mineral Density in Forensic Contexts
07:56

Scanning Skeletal Remains for Bone Mineral Density in Forensic Contexts

Published on: January 29, 2018

Z-score comparability of bone mineral density reference databases for children.

J Kocks1, K Ward, Z Mughal

  • 1Department of Pediatrics, Medical University Innsbruck, Innsbruck, Austria.

The Journal of Clinical Endocrinology and Metabolism
|July 30, 2010
PubMed
Summary

Pediatric bone mineral density (BMD) Z-scores from different Hologic dual-energy x-ray absorptiometry (DXA) databases show significant differences, potentially leading to misdiagnosis in children. Using specific reference curves is recommended for accurate BMD assessment.

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Last Updated: Jun 10, 2026

Scanning Skeletal Remains for Bone Mineral Density in Forensic Contexts
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Area of Science:

  • Pediatric endocrinology
  • Medical imaging
  • Bone densitometry

Background:

  • Dual-energy x-ray absorptiometry (DXA) is crucial for assessing bone mineral density (BMD) in children.
  • Variability in pediatric DXA reference databases raises concerns about diagnostic consistency.

Purpose of the Study:

  • To evaluate the comparability of BMD Z-scores derived from different Hologic DXA databases in pediatric patients.
  • To determine if these databases are interchangeable for clinical application.

Main Methods:

  • Analysis of 2027 BMD scans from Hologic QDR-4500A machines.
  • Calculation and comparison of age- and sex-specific BMD Z-scores using six Hologic databases for lumbar spine (LS) and total body (TB) in children aged 8-17 years.

Main Results:

  • BMD Z-scores showed high correlation but significant differences across databases (P < 0.001).
  • Interdatabase Z-score variations reached up to 1.0 in total body measurements.
  • The prevalence of low BMD for age (-2 or below) varied significantly, impacting diagnostic rates.

Conclusions:

  • Clinically significant differences exist between Hologic DXA databases, posing a risk of misdiagnosis in pediatric BMD assessment.
  • Utilizing model-, brand-, and software-specific reference curves is ideal for accurate Z-score calculation.
  • The study highlights limitations of DXA in detecting all aspects of bone health in children.