We quantified confidence intervals (CIs) for T-scores for the lumbar spine and hip and determined the practical effect (impact on diagnosis) of variability around the T-score cutpoint of -2.5. Using precision data from the literature for GE Lunar Prodigy dual-energy X-ray absorptiometry (DXA) systems, the 95% CI for the T-score was ±0.23 at the lumbar spine (L1-L4), ± 0.20 at the total hip, and ±0.41 at the femoral neck. Thus, T-score variations of ±0.23 or less at the spine, ±0.20 at the total hip, and ±0.41 at the femoral neck are not statistically significant. When diagnosing osteoporosis, T-scores in the interval -2.3 to -2.7 for spine or total hip (after rounding to conform to guidelines from the International Society for Clinical Densitometry) and -2.1 to -2.9 for femoral neck are not statistically different from -2.5. Better precision values resulted in smaller 95% CIs. This concept was applied to actual clinical data using Hologic DXA systems. The study cohort comprised 2388 white women with either normal or osteopenic spines in whom the densitometric diagnosis of osteoporosis would be determined by hip T-scores. When evaluating actual patient T-scores in the range -2.5 ± 95% CI, we found that the diagnosis was indeterminate in approximately 12% of women when T-scores for femoral neck were used and in 4% of women when T-scores for total hip were used, with uncertainty as to whether the classification was osteopenia or osteoporosis. We conclude that precision influences the variability around T-scores and that this variability affects the reliability of diagnostic classification.

Introduction: We determined the prevalence of left-right differences in hip bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) and the resultant consequence, namely: the frequency at which patients would be classified differently if lumbar spine and only one hip (rather than both hips) were measured. Methods: This was a retrospective DXA scan reanalysis of 3012 white women ≥50 yrs who had scans of both hips using Hologic DXA systems. The difference between left and right hips was considered significant if it exceeded the least significant change (LSC) for any of three hip subregions (total hip, femoral neck, trochanter). The number of women with osteoporosis in both hips, the left hip only, or the right hip only was determined by lowest T-score from total hip, femoral neck, or trochanter. Results: Despite high left-right correlations of subregion BMD, significant left-right differences in BMD were common: the difference exceeded the LSC for 47% of women at total hip, 31% at femoral neck, and 56% at trochanter. Left-right differences in BMD that exceeded the LSC affected the percent agreement of left-right hip classification: for all women irrespective of spine status, there was 77% classification (diagnostic) agreement in hip pairs in which the left-right hip BMD difference exceeded the LSC versus 87% agreement in which LSC was not exceeded (significant difference in proportions, P<0.0001). The greatest risk of different classification would occur in women with normal spines as the diagnosis might be determined by hip T-scores. Using L1-4 lumbar spine T-scores, 1229 women were normal at the spine. Twenty-four (2%) were osteoporotic at both hips. However, 12 women (1%) were osteoporotic only in the left hip (significantly different from zero, P<0.001) and 11 (1%) only in the right hip (P<0.001); of these 23 women, the difference in BMD between the osteoporotic hip and the contralateral hip exceeded the LSC in 16 (70% of those with osteoporosis in only one hip). Using L1-4 lumbar spine T-scores, 1159 women were osteopenic at the spine. Of these, 126 (11%) were osteoporotic at both hips, 54 (5%) only in the left hip (P<0.001), and 42 (4%) only in the right hip (P<0.001); of these 96 women, the difference in BMD between the osteoporotic hip and the contralateral hip exceeded the LSC in 56 (58% of those with osteoporosis in only one hip). Conclusions: A statistically significant number of women with osteoporosis are potentially classified differently when scanning only one hip as a result of the high prevalence of left-right differences in BMD. Although the percentages are low, the total number of women affected may be large. From a public health perspective, the practice of scanning both hips could potentially identify more women with osteoporosis and may help prevent future hip fractures. © 2006 International Osteoporosis Foundation and National Osteoporosis Foundation.

Introduction: Les personnes vivant avec le VIH (PVVIH) présentent des risques accrus d’ostéoporose et de lipodystrophie. Peu d’études se sont penchées sur l’association entre les déterminants du style de vie, le risque d’ostéoporose et le risque de lipodystrophie chez les PVVIH. Objectifs: L’objectif primaire était d’évaluer l’association entre l’ostéoporose, la lipodystrophie ainsi que différents déterminants du style de vie chez les PVVIH. Méthodologie: Tous les participants de la Cohorte canadienne VIH et vieillissement (CCVV) avec des données sur la densité minérale osseuse (DMO), mesurée par absortiométrie biphotonique à rayons X (DXA), ont été inclus dans cette étude transversale. Les déterminants du style de vie d’intérêt étaient : le revenu annuel, le niveau d’éducation, l’exercice physique ainsi que les consommations d’alcool, de tabac et de drogues illicites. Les covariables mesurées incluaient l’historique complet de la médication antirétrovirale, les comorbidités, les co-infections, la charge virale, le compte de CD4+ au recrutement et le compte de CD4+ nadir. L’ostéoporose a été définie par un score T de -2.5 ou moins. La lipodystrophie, évaluée par la composition corporelle via DXA, a été définie par un fat mass ratio (rapport des pourcentages de gras entre le tronc et les membres inférieurs) supérieur à 1.33 pour les femmes et 1.96 pour les hommes. Les rapports des cotes et les intervalles de confiance à 95% (IC95%) au recrutement ont été estimés en utilisant des régressions logistiques multivariées. Résultats: Nous avons inclus 547 PVVIH (âge médian 55 ans, 88% d’hommes) et 97 contrôles séronégatifs au VIH (âge médian 54 ans, 54% d’hommes). L’ostéoporose était présente chez 13% des PVVIH et 6% des contrôles (OR 2.21, IC 95% [0.96 – 6.06]). La lipodystrophie était présente chez 138 (28.3%, IC 95% 24.3 – 32.3%) des 487 PVVIH avec des données sur la disposition du gras corporel. Aucun des déterminants du style de vie était associé à l’ostéoporose ou à la lipodystrophie. Par contre, les covariables associées à un risque accru d’ostéoporose étaient l’âge avancé, un indice de masse corporelle (IMC) réduit et la co-infection à l’hépatite C. Les covariables associées au risque accru de lipodystrophie étaient l’âge avancé, l’hypertension, l’exposition prolongée aux antirétroviraux, ainsi que les expositions prolongées aux inhibiteurs nucléosidiques de la transcriptase inverse (INTI) et aux inhibiteurs de l’intégrase (INI). Conclusion: Aucune association n’a été décelée entre les déterminants du style de vie étudiés et l’ostéoporose ou la lipodystrophie. / Background: As a consequence of ART, people living with HIV (PLWH) are at higher risk for osteoporosis and lipodystrophy. However, the risk may also be influenced by lifestyle factors, but few studies have explored the association between modifiable lifestyle factors and the risk of osteoporosis or lipodystrophy in the PLWH population. Objectives: Our primary objective was to evaluate the lifestyle factors in relation to the risks of osteoporosis and lipodystrophy in a PLWH-based cohort. Methods: We conducted a cross-sectional analysis of data from the Canadian HIV and Aging Cohort Study (CHACS). We included all participants with available bone mineral density T-scores, which were measured by dual-energy X-ray absorptiometry (DXA) scans. Lifestyle risk factors of interest included annual income, education level, alcohol intake, tobacco use, illicit drug use and physical exercise. Other covariates considered were full antiretroviral medication history, medical comorbidities, coinfections, viral load, nadir CD4+ and current CD4+ count. Osteoporosis was defined by a T-score of -2.5 or lower at any of the measured sites. Lipodystrophy was assessed on whole body DXA and defined as a fat mass ratio (the ratio between trunk and lower limbs fat mass) greater than 1.33 for women and 1.96 for men. Baseline prevalence odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated by multivariate logistic regressions. Results: We included 547 PLWH (median age 55 years, 88% males) and 97 HIV-uninfected controls (median age 57 years, 64% males). Osteoporosis was present in 13.0% of PLWH (95% CI 10.2 – 15.8%) and 6% of controls (95% CI 1.4 – 11.0%); the OR of osteoporosis for HIV seropositivity was 2.21 (95% CI [0.96 – 6.06]). Lipodystrophy was found in 138 (28.3%, 95% CI 24.3 – 32.3%) of the 487 PLWH for which a fat mass ratio (FMR) was available. None of the lifestyle factors of interest were associated with osteoporosis or lipodystrophy. However, covariates associated with an increased risk of osteoporosis were increasing age, lower body mass index (BMI) and hepatitis C coinfection. Covariates associated with an increased risk of lipodystrophy were older age, hypertension, longer antiretroviral duration, and longer exposure to nucleoside reverse transcriptase inhibitors (NRTIs) and integrase strand inhibitors (INSTIs). Conclusion: No association was found between any of the lifestyle factors of interest and osteoporosis or lipodystrophy.