Effect of Precision on Longitudinal Follow-Up of Bone Mineral Density Measurements in Elderly Women and Men

Lenora, Janaka; Åkesson, Kristina; Gerdhem, Paul

doi:10.1016/j.jocd.2010.04.004

« Previous Next »Journal of Clinical Densitometry
Volume 13, Issue 4 , Pages 407-412, October 2010

Effect of Precision on Longitudinal Follow-Up of Bone Mineral Density Measurements in Elderly Women and Men

Janaka Lenora
- Department of Clinical Sciences, Clinical and Molecular Osteoporosis Research Unit, Lund University, Malmö, Sweden
- Department of Orthopaedics, Malmö University Hospital, Lund University, Malmö, Sweden
Kristina Åkesson
- Department of Clinical Sciences, Clinical and Molecular Osteoporosis Research Unit, Lund University, Malmö, Sweden
- Department of Orthopaedics, Malmö University Hospital, Lund University, Malmö, Sweden
- Address correspondence to: Kristina Åkesson, MD, PhD, Department of Orthopaedics, Malmö University Hospital, Lund University, SE-20502 Malmö, Sweden.
Paul Gerdhem
- Department of Clinical Science, Intervention and Technology, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
- Department of Orthopaedics, Karolinska University Hospital, Stockholm, Sweden

Received 14 October 2009; received in revised form 20 March 2010; accepted 21 April 2010. published online 07 June 2010.

Abstract

Precision error of dual-energy X-ray absorptiometry exceeds the expected annual rate of bone loss in the elderly. The capacity to detect changes in areal bone mineral density (aBMD; g/cm²) over a 5-yr period was assessed. Six hundred ninety-one women, 75.2 (0.1)yr, from the Malmö OPRA-study, were measured using Lunar DPX-L (GE Lunar, Madison, WI), and 211 men, 74.7 (3.2)yr, from the Malmö Mr Os-study, were measured using Lunar Prodigy (GE Lunar) with follow-up 5yr later. Precision error was determined with 30 degrees of freedom. Least significant change (LSC, i.e., 2.77×precision error) was calculated. Women's precision errors (g/cm²) for DPX-L were 0.028 (total hip [TH]) and 0.016 (lumbar spine [LS]), and for Prodigy, they were 0.009 (TH) and 0.039 (LS). In men, corresponding results for Prodigy were 0.014 and 0.031. In women, 41% and in men, 39% had aBMD changes exceeding the LSC at TH. Follow-up intervals (i.e., LSC/median rate of aBMD change) for both women and men were 8yr (TH) and 13yr (LS). Based on Prodigy precision data, follow-up intervals for women were 3 and 32yr at TH and LS. In summary, several years were needed to detect change. Only when a high rate of bone loss is suspected, a short follow-up time is possible, in elderly persons.