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Bone mineral density (BMD) measurements using dual-energy X-ray absorptiometry (DXA) are widely used to diagnose osteoporosis and assess its severity. Previous studies show the necessity to establish reference data for bone mass measurements for each particular population. Such data are lacking for the Moroccan population. The aim of this study was to determine spine and femur BMD reference values for the Moroccan female population and to compare them with values from western and other Arab countries. A cross-sectional study of 569 Moroccan women, (randomly selected in the area of Rabat, the capital of Morocco, aged between 20 and 79 yr) was carried out to establish reference values of BMD. Measurements were taken at the lumbar spine and proximal femurs using DXA (Lunar Prodigy Vision, GE). The data were compared with published normative data taken by United States (U.S.), European, Kuwaiti, Lebanese, and Saudi women over 6 decades of age. The percentage of osteoporosis in postmenopausal women using our reference curve was compared to that observed when the other curves (US, European and Arab) implemented in the Lunar machine was used. Our results showed that the Moroccan women showed the expected decline in BMD at both sites with age after peaking at 20-29 years of age. Moroccan females have lower BMD at the spine than U.S., Europeans, and Kuwaitis (approximately 10-12% for patients older than 50 yr). The BMD values of the total femur in Moroccan females were close to western (European and American), and Kuwaitis, but higher than Lebanese and Saudis. Using our reference database, 37.9% of postmenopausal women had spine osteoporosis vs. 39.6% and 23.4% using US/European and Arabic Lunar reference values respectively. At the femurs, 6.7% had osteoporosis vs. 2.5% using the Arabic Lunar reference values. In conclusion, our study emphasizes the importance of using population-specific reference values for BMD measurements to avoid over or underdiagnosis of osteoporosis.

Bone mineral density (BMD) measurements are frequently performed repeatedly for each patient. Subsequent BMD measurements allow reproducibility to be assessed. Previous studies have suggested that reproducibility may be influenced by age and clinical status. The purpose of the study was to examine the reproducibility of BMD by dual energy X-ray absorptiometry (DXA) and to investigate the practical value of different measures of reproducibility in three distinct groups of subjects: healthy young volunteers, postmenopausal women and patients with chronic rheumatic diseases. Two hundred twenty-two subjects underwent two subsequent BMD measurements of the spine and hip. There were 60 young healthy subjects, 102 postmenopausal women and 60 patients with chronic rheumatic diseases (33 rheumatoid arthritis, 10 ankylosing spondylitis and 10 other systemic diseases). Forty-five patients (75%) among the third group were receiving corticosteroids. Reproducibility was expressed as the smallest detectable difference (SDD), coefficient of variation (CV), least significant change (LSC) and intraclass correlation coefficient (ICC). Sources of variation were investigated by linear regression analysis. The median interval between measurements was 0 days (range 0-7). The mean difference (SD) between the measurements (g/cm2) was -0.0001 (+/-0.003) and -0.0004 (+/-0.002) at L1-L4 and the total hip, respectively. At L1-L4 and the total hip, SDD (g/cm2) was +/-0.04 and +/-0.02, CV (%) was 2.02 and 1.29, and LSC (%) 5.60 and 3.56, respectively. The ICC at the spine and hip was 0.99 and 0.99, respectively. Only a minimal difference existed between the groups. Reproducibility in the three groups studied was good. In a repeated DXA scan, a BMD change, the least significant change (LSC) or the SDD should be regarded as significant. Use of the SDD is preferable to use of the CV and LSC because of its independence from BMD and its expression in absolute units. Expressed as SDD, a BMD change of at least +/-0.04 g/cm2 at L1-L4 and +/-0.02 g/cm2 at the total hip should be considered significant. This reproducibility seems independent from age and clinical status and improved in the hips by measuring the dual femur.