Avoiding the under-diagnosis of low bone mineral density in Egyptian children with chronic medical conditions affecting bone health Table IV. Correlations between BMD and anthropometry in the studied group Item Femoral BMD Spine BMD HAZ WAZ BMI R P R P R P R P R P Femoral neck 0.000 0.648** 0.000 0.064 0.206 0.016 0.746 –0.079 0.118 Spine 0.648** 0.000 0.000 0.106 0.035 0.085 0.092 –0.087 0.085 HAZ 0.064 0.206 0.106 0.035 0.0 0.86** 0.000 0.079 0.099 WAZ 0.016 0.746 0.085 0.092 0.869** 0.000 0.0 0.485** 0.000 BMI –0.079 0.118 –0.087 0.085 0.079 0.099 0.485** 0.000 0.0 **means value is statistically significant, R – correlation coefficient, P – probability level, HAZ – height for age Z-score, WAZ – weight for age Z-score higher (40%) in children with JRA than healthy children (8%) (p = 0.013), and although the frequency was higher at the lumbar spine of the patients (26.7%) vs. controls (8%) it was not significant (p = 0.074), with no sex-related difference. Only 1 patient (3.3%) was found to have very low BMD (Z score < –2 SD) in the femoral neck [9]. Discussion The purpose of the current study was to evaluate the role of measurement of femoral neck BMD in avoiding the under-diagnosis of low BMD being a risk for fractures in subjects with chronic medical conditions that might affect bone health. In the present study, lumbar (L2-L4) and femoral neck BMD were analysed together in all cases and controls. The terms “osteopenia” and “osteo- porosis” should not be used in paediatric DXA reports because they refer specifically to WHO fracture risk criteria developed for postmenopausal women. There are no similar criteria for osteo- porosis based on BMD for children, adolescents, or premenopausal women [10]. Michael et al. (2008) reported that the term “osteoporosis” should not appear in paediatric DXA reports without knowledge of clinically significant fracture history [11]. Some studies found that it is reasonable to imagine that a Z score of –1 or less might be suggestive of the paediatric equivalent of osteopenia and a Z score of –2 or less suggestive of an osteoporosis equivalent [10, 11]. “Low bone mass for chronological age” is the preferred term when the BMC or BMD Z-score is less than or equal to –2.0 [12]. Although estimation of total body less head (TBLH) BMD is valuable in children, it was technically not feasible to estimate it in our study. Our DXA results were categorized according to the following cut-off points for children: the diagnosis of very low BMD defined as a BMD of 2 SD or more below the mean value (the Z score) compared to age- and sex-matched healthy controls. According to this approach, low BMD would be said to exist when the BMD Z score lies between –1 and –2 SD. So our study found that about 3.69% of our children with chronic diseases had very low BMD, while low BMD between –1 SD and –2 SD were 9.52%, 18.05% and 21.14% respectively. Also there is a correlation between the lumbar spine and femoral neck regions. Although BMDs of the lumbar spine and hip regions are strongly related in healthy children, considerable anatomical differences between the two sites may become apparent as BMD decreases [13]. The spine is formed mainly of trabecular bone, which has a higher surface-to-volume ratio and is more active metabolically than other regions of skeleton [5]. Because of the greater rapidity of bone turnover in the trabecular compartment than in the cortical one, the spine is thought to be a more sensitive site than the long bones of the upper and lower extremities for evaluating the effects of various stimuli on bone mineral status of the body [10, 14]. Previous studies have reported that the spine, which is predominantly trabecular bone, is more sensitive to various therapeutic modalities, including methotrexate and corticosteroids, than the femoral neck, which contains more cortical bone [15-17]. Van der Sluis et al. found that children with acute lymphoblastic leukaemia Disease- associated changes in the quantity and distribution of cortical and cancellous bone around the femoral neck might contribute to enhance hip fragility in osteoporosis bone fragility does not only result from cortical thinning but also from trabecular bone rarefaction associated with loss of trabecular connectivity [18-20]. In other cross-sectional studies, significant reductions in both lumbar and femoral BMDs were observed in children with acute lymphoblastic Arch Med Sci 4, August / 2011 703