Fracture Risk Assessment in African American Women Using Quantitative Ultrasound of the Os Calcis

Abstract

Osteoporosis is a disease characterized by reduced bone mass and quality with increased risk for fracture. While dual-energy X-ray absorptiometry (DXA) is typically used to assess bone density (BMD), the technique of quantitative ultrasound (QUS) allows for the assessment of bone quality or stiffness index (SI). PURPOSE: To examine bone quality and risk for osteoporotic fracture in African American women using quantitative ultrasound of the os calcis. METHODS: This investigation included two separate studies. First, T-score risk for fracture was compared between quantitative ultrasound (QUS) of the os calcis and dual-energy X-ray absorptiometry (DXA) of the dual femur and spine in a group of African American women forty years of age and older (n = 20). The definitions of low bone mass proposed by the world health organization were used to classify the women (T-score ≤ −1.0 = osteopenia and T-score ≤ −2.5 = osteoporosis). The QUS apparatus was an Achilles Insight (GE Medical Systems, Madison, WI) and the DXA device was a Prodigy Pro (GE Medical Systems, Madison, WI). Secondly, QUS measurement of the os calcis was used to screen for osteoporotic fracture in ambulatory African American women attending local community health fairs. RESULTS: In the first study, mean descriptives were: age = 55.2 ± 11.0 yrs, dual femur BMD = 1.000 ±0.181 g-cm-2, spine BMD = 1.180 ± 0.214 g-cm-2, os calcis SI = 97.4 ±21.6. The correlation between QUS SI and DXA BMD was greater with the dual femur (r = 0.78, p = 0.00) than with the spine BMD (r = 0.65, p = 0.00). The sensitivity in identifying risk for fracture (T-score <-1.0) was 100% between the QUS and DXA dual femur assessment and 80% compared to the DXA spine assessment. The specificity between the two machines was 87% with the dual femur and 86% with the spine assessment. In the second study, one hundred and nineteen women, 40 to 94 years of age (mean age = 64.3 ± 10.5 years) were measured. Mean SI value was 92 ± 21.9. Forty-two percent of the women were classified by SI T-score as having low bone quality with 5% in the osteoporotic fracture range. CONCLUSIONS: In a small group of African American women QUS and DXA assessments of bone quality appear to be very similar. Community screening using QUS suggests that a large percentage of African American women have reduced bone quality and may be at risk for future osteoporotic fracture.