Bone Density z-Score and Its Real Meaning

Bone Density is a medical term that means the amount of matter per square centimeter of bones. The procedure that is used to calculate the bone density is known as the densitometry. The procedure is generally performed in the radiological treatments or the nuclear medicinal treatments in various hospitals as well as clinics. The technology that is used to measure the bone density is known as the Dual Energy X-ray Absorptiometry or DEXA in short. A machine utilizing this technology is used in order to get the bone density. In this test the machine takes the picture of the bones in the hip, spine, wrists and the total body and then calculates their density.

The results of the test are most commonly reported in 3 terms:

  • It is measured g cm-3
  • z-score- The number of standard deviations above or below the mean for the patient's age, sex and ethnicity
  • t-score- The number of standard deviations above or below the mean for a healthy 30 year old adult of the same sex and ethnicity as the patient
 The bone density z-score is one of the most common scores that are used in the measurement of the bone density of an individual. It is basically the standard score that is quite common in the statistical parlance. The z-score is the one that is used in the z-test in the standardized testing. It is generally based on the estimate rather than a single entity. The bone density z-score is based on the understanding of the contributions that that are made by the various sub-sets of the bone density data to the overall test of the trend.

It is the standardization of the data that is collected from the various sources and then comparing it with the result that is obtained from the bone density test of the patient under observation.

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