Avoiding the under-diagnosis of low bone mineral density in Egyptian children with chronic medical conditions affecting bone health Moreover, the interpretation of densitometric data in the young is difficult because the “normal” BMD values to be used for comparison are continuously changing with age, and in addition depend on several variables, such as gender, body size, pubertal stage, skeletal maturation and ethnicity. Most methods to adjust bone mineral content (BMC)/BMD Z-scores for height were biased by age and/or height for age Z score (HAZ). Adjustments using HAZ were least biased relative to HAZ and age and can be used to evaluate the effect of short or tall stature on BMC/BMD Z-scores [4]. Although Z-score values below –2 are generally considered a serious warning, most bone specialists make a diagnosis of osteoporosis in children and adolescents only in the presence of low BMD and at least one fragility fracture [5]. Dual energy X-ray absorptiometry (DXA) is considered the gold standard of BMD measurement. The International Society for Clinical Densitometry Official Positions recommended that the lumbar spine and total body less head (TBLH) are the most accurate and reproducible skeletal sites for performing BMC and areal BMD measurements [6]. The aim of this study is to evaluate the role of measurement of femoral neck BMD in avoiding the under-diagnosis of low bone mineral density being a risk for fractures in subjects with chronic medical conditions that might affect bone health. Material and methods Study design A total of 700 patients were referred to the Pediatric Clinic at the National Research Centre (NRC) in the period from March 2005 to March 2009; of these 468 patients were included. Thirty-six healthy age- and sex-matched children were also included in the study, serving as a control group. Inclusion criteria Age 5 years or more because the femoral neck may be too small for the standard software and changing its shape makes studies difficult and unreliable for younger children. Exclusion criteria – Children with conditions preventing or limiting the use of standard measurement sites or positioning for densitometry evaluation such as scoliosis, or altered body postures or muscular contractures that prevent them from lying flat in a supine position for optimal measurement of the spine or hip. – Artefacts and abnormalities in spinal vertebra. – Parents refused inclusion in the study. Arch Med Sci 4, August / 2011 So the study was conducted on 504 subjects including 36 healthy controls and 468 patients with chronic diseases: bronchial asthma, diabetes mellitus, congenital adrenal hyperplasia, chronic renal failure, nephrotic syndrome, chronic liver diseases, coeliac disease, juvenile rheumatoid arthritis (JRA), mucopolysacharidosis, hypothyro- idism, chronic haemolytic anaemia, and phenyl- ketonuria (Table I). Methods Informed consent was obtained from the parents of the children according to guidelines of the ethical committee of NRC, Dokki, Egypt. All patients were subjected to full history taking and general examination. Anthropometric measurements Anthropometric measurements (height and weight) were measured. Weight was measured using a standard clinical balance (weight was approximated to the nearest 0.1 kg) and height was measured using a fixed stadiometer (height was approximated to the nearest millimetre). All measurements were made with the children wearing light indoor clothes without their shoes. Body mass index (BMI) was calculated as weight divided by height squared (kg/m2). Pubertal status was determined and classified according to Tanner stages as prepubertal (stage I), early puberty (stages II and III) and late puberty (stages IV and V) [7]. Bone mineral measurements Bone mineral measurements were done using dual energy X-ray absorptiometry (DXA) (Norland – Table I. Diagnosis of the studied group Cases Coeliac disease Chronic liver disease Bronchial asthma Chronic renal failure Chronic Hm anaemia Juvenile rheumatoid arthritis (JRA) Suprarenal hyperplasia Thyroid diseases Metabolic disorders Nephrotic Pts treated with corticosteroids Type 1 diabetes Phenylketonuria Mucopolysacharidosis Control Total No. 25 25 80 65 30 30 30 35 50 30 35 25 8 36 504 701