Response to "The Perspective of the International Osteoporosis Foundation on the Official Positions of the International Society for Clinical Densitometry," by John A. Kanis et al.
ABSTRACT We greatly appreciate the thoughtful perspective by Kanis and colleagues regarding the Official Positions of the International Society for Clinical Densitometry (ISCD), published in their entirety in the Journal of Clinical Densitometry (1) and summarized in the Journal of Clinical Endocrinology and Metabolism (2) and Osteoporosis International (3). A robust scientific debate on the clinical applications of bone density testing is desirable and necessary. It is only through open discussion of diverse viewpoints that we will coherently define the clinical utility of bone densitometry. The development of practical standards by which health care practitioners can be guided is a major step toward improving patient care worldwide.
SourceAvailable from: John J Carey
Article: T-Scores and Z-Scores[Show abstract] [Hide abstract]
ABSTRACT: Bone mineral density (BMD) can be measured by a variety of techniques at several skeletal sites. Once measured, the manufacturers’ software uses the BMD to calculate a T-score and/or Z-score. Both T-scores and Z-scores are derived by comparison to a reference population on a standard deviation scale. The recommended reference group for the T-score is a young gender-matched population at peak bone mass, while the Z-score should be derived from an age-matched reference population. T-scores and Z-scores are widely quoted in scientific publications on osteoporosis and BMD studies, and are the values used for DXA diagnostic criteria and current clinical guidelines for the management of osteoporosis. Errors in BMD measurement, differences in reference populations, and variations in calculation methods used, can all affect the actual T-score and Z-score value. Attempts to standardize these values have made considerable progress, but inconsistencies remain within and across BMD technologies. This can be a source of confusion for clinicians interpreting BMD results. A clear understanding of T-scores and Z-scores is essential for correct interpretation of BMD studies in clinical practice. KeywordsDXA-Bone mineral density- T-score- Z-scoreClinical Reviews in Bone and Mineral Metabolism 09/2009; 8(3):113-121. DOI:10.1007/s12018-009-9064-4
[Show abstract] [Hide abstract]
ABSTRACT: Objective There is a variable body of evidence on adverse bone outcomes in HIV patients co-infected with hepatitis C virus (HCV). We examined the association of HIV/HCV co-infection on osteoporosis or osteopenia (reduced bone mineral density; BMD) and fracture. Design Systematic review and random effects meta-analyses. Methods A systematic literature search was conducted for articles published in English up to 1 April 2013. All studies reporting either BMD (g/cm2, or as a T-score) or incident fractures in HIV/HCV co-infected patients compared to either HIV mono-infected or HIV/HCV uninfected/seronegative controls were included. Random effects meta-analyses estimated the pooled odds ratio (OR) and the relative risk (RR) and associated 95% confidence intervals (CI). Results Thirteen eligible publications (BMD N = 6; Fracture = 7) of 2,064 identified were included with a total of 427,352 subjects. No publications reported data on HCV mono-infected controls. Meta-analysis of cross-sectional studies confirmed that low bone mineral density was increasingly prevalent among co-infected patients compared to HIV mono-infected controls (pooled OR 1.98, 95% CI 1.18, 3.31) but not those uninfected (pooled OR 1.47, 95% CI 0.78, 2.78). Significant association between co-infection and fracture was found compared to HIV mono-infected from cohort and case-control studies (pooled RR 1.57, 95% CI 1.33, 1.86) and compared to HIV/HCV uninfected from cohort (pooled RR 2.46, 95% CI 1.03, 3.88) and cross-sectional studies (pooled OR 2.30, 95% CI 2.09, 2.23). Conclusions The associations of co-infection with prevalent low BMD and risk of fracture are confirmed in this meta-analysis. Although the mechanisms of HIV/HCV co-infection’s effect on BMD and fracture are not well understood, there is evidence to suggest that adverse outcomes among HIV/HCV co-infected patients are substantial.PLoS ONE 07/2014; 9(7):e101493. DOI:10.1371/journal.pone.0101493 · 3.53 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Dual-energy X-ray Absorptiometry (DXA) is considered the gold standard for non-invasive measurement of bone mass. T-scores and Z-scores are used to present the results of bone mass. The present study was designed to evaluate the discordance between T-scores and Z-scores calculated at a same level and its relation with age, gender and body mass index (BMI) in a representative sample of normal population. This cross-sectional study was conducted as a part of a comprehensive survey, Iranian Multicenter Osteoporosis Study (IMOS), designed to assess bone health among healthy adults. Each individual underwent both L1-L4 antero-posterior lumbar spine and hip DXA scan. The difference between the T- and Z-scores measured at each of the four skeletal sites was then calculated. A -1.21 to 1.21 point difference was noted in the Z- and T- scores measured at each site. While the difference between the T-and Z-scores was less than 0.5 SD in most of the cases, the difference was higher than 1 SD in about 5% of the subjects. Standardization of Z-score definition and calculation techniques as well as developing an ethnicity-matched reference population is needed to improve the reliability of DXA-generated Z-scores.Medical journal of the Islamic Republic of Iran 01/2014; 28:151.