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| ISCD |
International Society for Clinical Densitometry
This non-profit medical society dedicated to high quality in the field of bone densitometry. |
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| DXA |
Dual Energy X-ray Absorptiometry
This is the most common technology for measuring BMD of the spine, hip, or forearm. |
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| ROI |
Region of Interest
A portion of the skeletal site selected for BMD measurement, such as femoral neck or trochanter. |
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| BMD |
Bone Mineral Density
Expressed as g/cm2 when measured by DXA. |
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| SD |
Standard Deviation
This is calculated for the BMD values of each patient. |
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| SD sq |
Sum of SD sq Values
The total of SD sq values for 15 patients tested 3 times each, or 30 patients tested 2 times each. |
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| N |
Number of Patients
This is usually15 or 30 for precision testing.
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| Sum/n |
Sum of SD sq Values Divided by the Number of Patients Tested |
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| SqRT |
Square Root of Sum/n |
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| PE |
Precision Error
This may be expressed as RMS SD, CV, or %CV. RMS SD is recommended. |
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| RMS SD |
Root Mean Square Standard Deviation
The standard deviation of the group, and the preferred method of expressing precision error, in g/cm2. |
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| CV |
Coefficient of Variation
SD divided by the mean BMD. Not advised for expressing precision error. |
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| %CV |
Percent Coefficient of Variation
CVx100%. Not advised for expressing precision error. |
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| CL |
Confidence Level
The ISCD recommends a 95% confidence level for establishing statistical significances for serial BMD testing. |
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| LSC |
Least Significant Change
This value is calculated by multiplying the precision error by 2.77 for a 95% confidence level. For a BMD change to be considered statistically significant, it must equal or exceed the LSC. LSC should be calculated with a new DXA instrument, and whenever it is moved to a new room or location. |
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| FAQ |
Frequently Asked Questions
Click this link to view commonly asked questions about precision assessment and the precision calculator. |
