Sievänen H, Backström M C, Kuusela A L, Ikonen R S, Mäki M
The Bone Research Group, UKK Institute, Tampere, Finland.
Pediatr Res. 1999 Jan;45(1):100-5. doi: 10.1203/00006450-199901000-00017.
The objective of this study was to evaluate the performance of dual energy x-ray absorptiometry (DXA) in forearm measurements of preterm and newborn term infants. The accuracy and linearity of DXA in measuring low mineral content levels (ranging from 30 to 300 mg) was assessed using bone-simulating K2HPO4 phantoms. For in vivo precision, DXA was performed twice on left forearms of four new-born term babies, 21 preterm infants at corrected age 3 mo, and 20 at corrected age 6 mo. Bone mineral content (BMC in mg) and areal bone mineral density (BMD in mg/cm2) at distal forearm and forearm shaft were measured. A special software program allowing a free adjustment of the bone detection threshold was used in the analysis of the scan data. The threshold level affected the overall ability of analysis to detect bone tissue and altered significantly the BMC and BMD values too. Given absolute success in detecting low amounts of bone mineral (BMC > 100 mg), the lowest bone detection threshold evaluated (0.040 g/cm2) became the preferable choice. The relationships between the actual and measured data were highly linear (r was 0.94 for BMC and 0.97 for BMD) but showed underestimation (corresponding slopes were 0.66 and 0.64). In vivo precision expressed as 95% limits of agreement was approximately +/-45 mg for BMC and +/-16 mg/cm2 for BMD. We conclude that DXA provides adequate reliability for in vivo determinations of BMC and areal BMD in the distal and shaft sites of forearm in term and preterm infants and thus strongly supports the clinical utility of DXA in the diagnosis and monitoring of metabolic disease of prematurity. Movements during scanning are typical of pediatric measurements and may decrease the precision considerably. Therefore, every effort must be made to prevent movement artefacts. In addition, special attention must be paid to keeping the analysis procedures consistent.
本研究的目的是评估双能X线吸收法（DXA）在前臂测量早产和足月新生儿中的性能。使用骨模拟K2HPO4体模评估DXA测量低矿物质含量水平（范围为30至300毫克）的准确性和线性。为了评估体内精密度，对4名足月新生儿、21名矫正年龄为3个月的早产儿和20名矫正年龄为6个月的早产儿的左前臂进行了两次DXA检查。测量了前臂远端和前臂骨干的骨矿物质含量（BMC，单位为毫克）和骨面积密度（BMD，单位为毫克/平方厘米）。在扫描数据分析中使用了一个允许自由调整骨检测阈值的特殊软件程序。阈值水平影响分析检测骨组织的整体能力，也显著改变了BMC和BMD值。鉴于在检测低骨矿物质含量（BMC>100毫克）方面取得了绝对成功，评估的最低骨检测阈值（0.040克/平方厘米）成为了首选。实际数据与测量数据之间的关系高度线性（BMC的r为0.94，BMD的r为0.97），但存在低估（相应斜率分别为0.66和0.64）。以95%一致性界限表示的体内精密度，BMC约为±45毫克，BMD约为±16毫克/平方厘米。我们得出结论，DXA为足月和早产儿前臂远端和骨干部位的BMC和骨面积BMD的体内测定提供了足够的可靠性，因此有力地支持了DXA在早产代谢性疾病诊断和监测中的临床应用。扫描过程中的移动是儿科测量中的典型情况，可能会显著降低精密度。因此，必须尽一切努力防止移动伪影。此外，必须特别注意保持分析程序的一致性。
