Bone Density Testing

Bone densitometry (BD) or central dual-energy x-ray absorptiometry (DEXA), has become an established and a well-known tool for diagnosing and following up patients with disorders affecting the bone mineralization such as osteoporosis or osteopenia.
Osteoporosis has been defined as a condition characterized by low bone mass and deterioration of bone tissue, leading to enhanced bone fragility and increase in fracture risk.
Osteopenia refers to decreased calcification or density of the bone.
DEXA results are measured in units of grams per square centimeter (g/cm2 ) and are expressed as a "Z score" and a "T score".
The value tested on an individual is compared to others' of the same age, sex, and race.This is called the Z-score. It is given in standard deviations (SD) from the average value for the specific age group.A negative (–) value indicates that an individual has thinner bones (lower bone density) than the average of people in their group.A positive (+) value indicates that one has higher bone density than the average of people in the group.In BD, the T-score is expressed as a standard deviation (SD), which is a statistical measure of how closely each person in a group is to the average (mean) of the group. The average BD is determined by measuring the bone density of a large group of healthy 30-year-olds (young adult reference range).BD values are then reported
as a standard deviation from the mean of this reference group. About 90% of people have a BD value within 2 standard deviations of this mean.Once again a negative value indicates that one has thinner bones (lower bone density) than an average 30-year-old and a positive value indicates that he/she has higher bone density than an average 30-year-old.
The results are interpreted as follows:
BD value in relation to young adult mean Classification

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