Zimmermann M B, Molinari L, Spehl M, Weidinger-Toth J, Podoba J, Hess S, Delange F
The Laboratory for Human Nutrition, Swiss Federal Institute of Technology, Zurich, Switzerland.
Eur J Endocrinol. 2001 Mar;144(3):213-20. doi: 10.1530/eje.0.1440213.
Interpretation of thyroid ultrasonography for assessing goiter prevalence requires valid reference criteria from iodine-sufficient populations. Reports have suggested the current reference criteria for thyroid volume (T(vol)) of WHO/ICCIDD (International Council for the Control of Iodine Deficiency Disorders) may be too high. Our objective was to determine if inter-observer and/or inter-equipment variability contributes to the disagreement in sonographic T(vol) in children reported from iodine-sufficient areas.
A 2-day workshop in which four experienced ultrasound examiners from around Europe measured T(vol) in 45 6--12-year-old Swiss schoolchildren using four different portable ultrasound machines. One of the participating examiners (observer A) had generated the T(vol) data in European children that are the basis for the WHO/ICCIDD reference criteria.
Sonographic T(vol) was measured in each child by all four examiners on all four machines. Six hundred and eighty-four examinations were completed, with examiners having no knowledge of one another's results. Inter-observer and inter-equipment variation was calculated.
Mean inter-equipment variation in T(vol) was 15.2% (95% CI: 14.1, 16.3%). There were no significant differences in T(vol) between equipment (P=0.51). For all observers, the mean inter-observer variation in T(vol) was 25.6% (95% CI: 23.9, 27.2%). At all ages and all body surface areas, there was a large systematic measurement bias (+30% volume) between the mean T(vol) of observer A and the mean Tvol of observers B, C and D. Reanalysis using data from observers B, C and D reduced the mean inter-observer variation in T(vol) to 13.3% (95% CI: 11.9, 14.7%). A correction factor for the systematic difference of operator A for the P50 and P97 of T(vol) was estimated using analysis of covariance. When applied to the WHO/ICCIDD reference data, it sharply reduced the discrepancy between the WHO/ICCIDD criteria and those from other iodine-sufficient children around the world.
Inter-equipment error contributes minimally to reported differences in sonographic T(vol). Even among experienced examiners, inter-observer variation in sonographic T(vol) in children can be high, and probably contributes to the current disagreement on normative values in iodine-sufficient children. A systematic bias at least partially explains why the WHO/ICCIDD reference data differ from those reported from other iodine-sufficient children around the world. The findings argue strongly for the standardization of methods used for sonographic measurement of T(vol) in children.
解读甲状腺超声检查以评估甲状腺肿患病率需要碘充足人群的有效参考标准。有报告表明，世界卫生组织/国际控制碘缺乏病理事会（ICCIDD）当前的甲状腺体积（T(vol)）参考标准可能过高。我们的目的是确定观察者间和/或设备间的变异性是否导致了碘充足地区报告的儿童超声T(vol)测量结果不一致。
举行为期两天的研讨会，来自欧洲各地的四名经验丰富的超声检查人员使用四台不同的便携式超声仪测量了45名6至12岁瑞士学童的T(vol)。参与的检查人员之一（观察者A）曾在欧洲儿童中生成T(vol)数据，这些数据是世界卫生组织/国际控制碘缺乏病理事会参考标准的基础。
所有四名检查人员使用所有四台仪器对每个儿童进行超声T(vol)测量。共完成了684次检查，检查人员彼此不知对方的测量结果。计算观察者间和设备间的变异性。
T(vol)的平均设备间变异性为15.2%（95%置信区间：14.1，16.3%）。不同设备间的T(vol)无显著差异（P = 0.51）。对于所有观察者，T(vol)的平均观察者间变异性为25.6%（95%置信区间：23.9，27.2%）。在所有年龄和所有体表面积组中，观察者A的平均T(vol)与观察者B、C和D的平均T(vol)之间存在较大的系统测量偏差（体积增加30%）。使用观察者B、C和D的数据重新分析后，T(vol)的平均观察者间变异性降至13.3%（95%置信区间：11.9，14.7%）。使用协方差分析估计了操作者A在T(vol)的P50和P97上的系统差异校正因子。将其应用于世界卫生组织/国际控制碘缺乏病理事会的参考数据时，显著减少了世界卫生组织/国际控制碘缺乏病理事会标准与世界其他碘充足儿童标准之间的差异。
设备间误差对报告的超声T(vol)差异影响极小。即使在经验丰富的检查人员中，儿童超声T(vol)的观察者间变异性也可能很大，这可能是目前碘充足儿童正常参考值存在分歧的原因。系统偏差至少部分解释了为什么世界卫生组织/国际控制碘缺乏病理事会的参考数据与世界其他碘充足儿童报告的数据不同。这些发现有力地支持了儿童超声测量T(vol)方法的标准化。
