|ISCD||International Society for Clinical Densitometry
This non-profit medical society dedicated to high quality in the field of bone densitometry.
|DXA||Dual Energy X-ray Absorptiometry
This is the most common technology for measuring BMD of the spine, hip, or forearm.
|ROI||Region of Interest
A portion of the skeletal site selected for BMD measurement, such as femoral neck or trochanter.
|BMD||Bone Mineral Density
Expressed as g/cm2 when measured by DXA.
This is calculated for the BMD values of each patient.
|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.
|N||Number of Patients
This is usually15 or 30 for precision testing.
|Sum/n||Sum of SD sq Values Divided by the Number of Patients Tested|
|SqRT||Square Root of Sum/n|
This may be expressed as RMS SD, CV, or %CV. RMS SD is recommended.
|RMS SD||Root Mean Square Standard Deviation
The standard deviation of the group, and the preferred method of expressing precision error, in g/cm2.
|CV||Coefficient of Variation
SD divided by the mean BMD. Not advised for expressing precision error.
|%CV||Percent Coefficient of Variation
CVx100%. Not advised for expressing precision error.
The ISCD recommends a 95% confidence level for establishing statistical significances for serial BMD testing.
|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.
|FAQ||Frequently Asked Questions
Click this link to view commonly asked questions about precision assessment and the precision calculator.