Dual-Energy X-Ray Absorptiometry Technical Issues: The 2007 ISCD Official Positions

Abstract

At the 2007 Position Development Conference, the Dual-Energy X-ray Absorptiometry Technical Task Force investigated three major areas of bone density testing. Although bone mineral density (BMD) testing in men had previously been reviewed at the 2005 Position Development Conference, we reviewed the most recent data in men to develop appropriate indications for bone density testing in men. We continue to recommend screening at age 70 and discuss the clinical risk factors that may be an appropriate indication for earlier BMD testing.

Menopausal transition (perimenopause) was considered an important time to consider BMD evaluation because bone loss may be significant prior to menopause. However, because fracture risk is inherently low in women of this age without other risk factors, screening BMD testing is not appropriate. We discuss the risk factors that are strong indicators of fracture risk that may be increased during the menopause transition. The presence of these risk factors are appropriate indications for BMD testing with applicability of WHO diagnostic categorization.

The issue of establishing a high threshold for BMD was investigated thoroughly and the current literature was reviewed. Despite the fact there is agreement that all BMD values greater than T-score -1.0 are not normal, it was felt that because of the paucity of sensitivity data and confounding factors such as high body mass index, an upper threshold could not be established or recommended at this time. This was felt to be an important area for further research.

Introduction

Three specific areas were identified for the Technical Task Force to review at the 2007 Position Development Conference. These include a review of bone density testing indications in men, women at menopause transition, and the question of unusually high bone mineral density.

Bone density testing in men has been underutilized for a number of reasons, including the uncertainty of the bone density fracture risk relationship in men. Although the previous Position Development Conference in 2005 (1), addressed the need for bone density testing in men and recommended testing for men at age 70, we propose recommendations for bone density testing in younger men. A significant challenge remains in diagnosing osteoporosis in a younger male and the World Health Organization (WHO) diagnostic criteria cannot be applied in the absence of clinical fragility fracture. We did define specific risk factors in younger men, however, that are appropriate indications for bone density testing, including current cigarette smoking (2), excessive alcohol use (>2 units/day average) (3), prior fracture (4), use of glucocorticoid medication (5), hypogonadism 6, 7, 8, 9 (endogenous or androgen deprivation therapy), and vitamin D deficiency.

Women in menopause transition are known to be at high risk for accelerated bone loss 10, 11, but generally low absolute risk of fracture. However, there are women in this stage of life who are at unusually high risk for fracture and we propose guidelines to help identify these women and consider them appropriate for bone density testing with dual-energy X-ray absorptiometry (DXA). Hypogonadism remains the most consistent predictor of bone loss although other risk factors are considered important including body weight, exercise habits, and prior fragility fracture. A large prospective Dutch study of women aged 46–54 provides us with important prevalence data (12). As women entered menopause, the prevalence of osteoporosis increased from 4.1% to 12.7%, and osteopenia increased from 27% to 42.8%. Fracture rates remained low, however, and we do not feel screening bone density testing is appropriate at menopause transition. When bone density testing is done, however, because the menopause transition is by definition characterized by hypogonadism, the WHO diagnostic categories for postmenopausal women are applied.

For the first time, the Position Development Conference reviewed the question of establishing a high threshold for ‘normal’ bone density values. There is evidence from the pediatric and adult literature that a number of disease states are associated with unusually high bone density values, and some are not protective to bone and in fact may be osteosclerotic pathology that increases fracture risk (13). Examples include osteopetrosis, Paget's Disease 14, 15, fluoride toxicity, and a variety of genetic disorders. More common, are degenerative changes that spuriously elevate bone density but are not necessarily associated with increased fracture risk 16, 17, 18. High body mass index is strongly associated with higher than average bone density, and has not been documented to increase fracture risk. The problem with establishing an upper threshold for bone density interpretation is the lack of sensitivity for pathologic states that warrant further evaluation and are associated with increased fracture risk. How many patients would need a ‘workup’ to identify an unusual pathology increasing fracture risk, and what would the ‘workup’ entail? Because of the number of unanswered questions, no consensus could be reached on establishment of an upper limit of ‘normal’ bone density.