Instant Vertebral Assessment: A Noninvasive Dual X-ray Absorptiometry Technique to Avoid Misclassification and Clinical Mismanagement of Osteoporosis

The presence of a vertebral fracture significantly increases the risk of future fracture, classifies a patient with "clinical" osteoporosis, and usually results in treatment for osteoporosis. However, the majority of vertebral fractures are silent, and lateral X-rays (the standard method for identification) are not routinely obtained. Instant vertebral assessment (IVA), a technology that utilizes dual X-ray absorptiometry (DXA), provides rapid assessment of vertebral fractures and is highly correlated with vertebral fractures, as assessed on standard lateral spine X-rays. To assess the role of IVA in patient management, we examined standard bone mineral density (BMD) of the spine, total hip, and femoral neck and spine IVA by DXA in 482 participants screened for an osteoporosis study, who had no previous knowledge of vertebral fractures. Using World Health Organization (WHO) guidelines, subjects were classified using BMD at the spine, total hip, femoral neck, or any combination of these central sites. In addition, we considered subjects as osteoporotic if they had vertebral fractures independent of low bone density. We found that vertebral fractures assessed by IVA were present in 18.3% of asymptomatic postmenopausal women recruited for this study. The sensitivity of BMD alone to diagnose osteoporosis based on either a vertebral fracture or low BMD using WHO criteria ranged from 40 to 74%. This means that between 26 and 60% of osteoporotic individuals could have potentially been missed. Furthermore, 11.0-18.7% of clinically osteoporotic individuals would have been classified as normal by BMD criteria alone. We conclude that IVA is a useful adjunct in the clinical identification of osteoporosis and may prevent mismanagement of osteoporotic patients.     

Taxation and its effect upon public and private health insurance and medical demand.

Multiple tax subsidies are available to many buyers and sellers of health insurance. These subsidies have the potential of creating excess demand for health insurance, which in turn can create excess demand for health services. A review of the literature on the effects of the tax subsidies on the price of health care shows that these subsidies, by raising prices in the medical sector, constrain the Medicare and Medicaid programs' ability to provide access to care for their beneficiaries.     

Absence of Langerhans cells in oral hairy leukoplakia, an AIDS-associated lesion

Oral hairy leukoplakia (HL) is a recently described manifestation of human immunodeficiency virus (HIV) infection in which Epstein-Barr virus (EBV) has been shown to replicate. To seek evidence for a local defect in mucosal immunity, we assessed the presence of epithelial Langerhans cells (LC) in these lesions and in autologous nonlesional mucosa. We used monoclonal antibodies against HLA-DR, HLA-DQ, and T6 antigens to identify LC in biopsy specimens of HL from 23 homosexual men. In all lesion specimens, LC either were not detected or were present only in greatly reduced numbers with at least 1 of the antibodies. In nonlesional oral mucosa from the same patients, LC were detected with all 3 antibodies in 11/12 specimens (92%) and were found in approximately normal numbers with at least 1 antibody. There was close correlation between the absence of LC and positive staining for EBV, human papillomavirus antigens, and candidal hyphae in the epithelium. We conclude that LC are absent or greatly reduced in the lesions of HL. Absence of normal LC function may be important in the pathogenesis of HL and may reflect an event in the pathogenesis of other features of the acquired immune deficiency syndrome.     

Construction of an extended three-dimensional idiotope map by electron microscopic analysis of idiotope-anti-idiotope complexes.

A three-dimensional map of the positions of four idiotypic determinants (idiotopes or Ids) and an isotypic determinant was derived by transmission electron microscopy of negatively stained immune complexes. Each complex was composed of a monoclonal Id-expressing IgG and one or two varieties of monoclonal anti-Id (or anti-isotype) Fab fragment or IgG. Data from the various combinations of Id and anti-Id (and anti-isotype) were used to construct a low-resolution three-dimensional model that revealed not only the approximate locations of Ids on the surface of the antibody variable domains but also details of the geometry of Id-anti-Id interactions not otherwise available. The Ids were shown to be dispersed over the variable domains, extending from the complementarity-determining region to near the variable-constant switch region. Thus, immunoelectron microscopy is a useful complement to serologic, biochemical, and genetic strategies for the topographical analysis of immunoglobulin Ids or other epitopes. This same approach should be of broader applicability in the study of epitopes and receptor sites on other macromolecules.