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The Importance of Precision

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Bone Densitometry for Technologists

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Abstract

Precision is the attribute of a quantitative measurement technique like bone densitometry that refers to the ability to reproduce the same numerical result in the setting of no real biologic change when the test is repeatedly performed in an identical fashion. Like all quantitative tests in clinical medicine, no bone densitometry technique is perfectly reproducible. This is true even when the bone density test is performed in exact accordance with the manufacturer’s recommendations every time. If the test is not consistently performed in accordance with the manufacturer’s recommendations, the technique becomes less reproducible.

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Notes

  1. 1.

     The term “precision error” is used interchangeably with precision.

  2. 2.

     The Gaussian distribution is the symmetrical bell-shaped curve that is obtained from a plot of values of a variable in which the variation in the value is caused by several independent factors. It was named after Gauss, the individual who originally described it. If the variation in the value of a variable is primarily from only one factor, the distribution will not be a symmetrical bell-shaped curve. Instead, it may be skewed in one direction or the other.

  3. 3.

     See Appendix C.

  4. 4.

     Although the RMS-SD is preferred to the RMS-%CV, the change in bone density from baseline seen with various therapeutic agents is generally given as a percentage in the medical literature, necessitating the use of the RMS-%CV for the calculation of the time to the LSC.

  5. 5.

     The ISCD precision calculator may be found at http://www.iscd.org. This calculator runs within Microsoft® Excel and may be downloaded at no cost. The program is available in English, Spanish, French, Portuguese, and Chinese. An advanced precision calculator is also available which allows the user to calculate the LSC at 80 %, 85 %, and 90 %, in addition to the recommended level of 95 %.

  6. 6.

     The 2010 guidelines from NAMS note that peripheral sites have “limited or no value” in the context of monitoring.

  7. 7.

     The most recent ISCD positions on bone density testing in 2007 incorporate the recommendations from earlier position papers and may be reviewed in Appendix C.

  8. 8.

     See Appendices C and E.

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Authors and Affiliations

  1. Clinical Research Center of North Texas, Denton, TX, USA

    Sydney Lou Bonnick MD, FACP, CCD & Lori Ann Lewis MRT, CDT

Authors
  1. Sydney Lou Bonnick MD, FACP, CCD
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  2. Lori Ann Lewis MRT, CDT
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Bonnick, S.L., Lewis, L.A. (2013). The Importance of Precision. In: Bone Densitometry for Technologists. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-3625-6_7

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  • DOI: https://doi.org/10.1007/978-1-4614-3625-6_7

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