Deitchler Megan, Valadez Joseph J, Egge Kari, Fernandez Soledad, Hennigan Mary
Academy for Educational Development, FANTA Project, Washington DC 20009, USA.
Int J Epidemiol. 2007 Aug;36(4):858-64. doi: 10.1093/ije/dym092. Epub 2007 May 21.
The conventional method for assessing the prevalence of Global Acute Malnutrition (GAM) in emergency settings is the 30 x 30 cluster-survey. This study describes alternative approaches: three Lot Quality Assurance Sampling (LQAS) designs to assess GAM. The LQAS designs were field-tested and their results compared with those from a 30 x 30 cluster-survey.
Computer simulations confirmed that small clusters instead of a simple random sample could be used for LQAS assessments of GAM. Three LQAS designs were developed (33 x 6, 67 x 3, Sequential design) to assess GAM thresholds of 10, 15 and 20%. The designs were field-tested simultaneously with a 30 x 30 cluster-survey in Siraro, Ethiopia during June 2003. Using a nested study design, anthropometric, morbidity and vaccination data were collected on all children 6-59 months in sampled households. Hypothesis tests about GAM thresholds were conducted for each LQAS design. Point estimates were obtained for the 30 x 30 cluster-survey and the 33 x 6 and 67 x 3 LQAS designs.
Hypothesis tests showed GAM as <10% for the 33 x 6 design and GAM as > or =10% for the 67 x 3 and Sequential designs. Point estimates for the 33 x 6 and 67 x 3 designs were similar to those of the 30 x 30 cluster-survey for GAM (6.7%, CI = 3.2-10.2%; 8.2%, CI = 4.3-12.1%, 7.4%, CI = 4.8-9.9%) and all other indicators. The CIs for the LQAS designs were only slightly wider than the CIs for the 30 x 30 cluster-survey; yet the LQAS designs required substantially less time to administer.
The LQAS designs provide statistically appropriate alternatives to the more time-consuming 30 x 30 cluster-survey. However, additional field-testing is needed using independent samples rather than a nested study design.
在紧急情况下评估全球急性营养不良（GAM）患病率的传统方法是30×30整群抽样调查。本研究描述了替代方法：三种用于评估GAM的批量质量保证抽样（LQAS）设计。对LQAS设计进行了现场测试，并将其结果与30×30整群抽样调查的结果进行了比较。
计算机模拟证实，小整群而非简单随机样本可用于GAM的LQAS评估。开发了三种LQAS设计（33×6、67×3、序贯设计）以评估10%、15%和20%的GAM阈值。2003年6月，在埃塞俄比亚的西拉罗，这些设计与30×30整群抽样调查同时进行了现场测试。采用嵌套研究设计，收集了抽样家庭中所有6至59个月儿童的人体测量、发病率和疫苗接种数据。对每种LQAS设计进行了关于GAM阈值的假设检验。获得了30×30整群抽样调查以及33×6和67×3 LQAS设计的点估计值。
假设检验表明，33×6设计的GAM＜10%，67×3和序贯设计的GAM≥10%。33×6和67×3设计的GAM点估计值（6.7%，CI = 3.2 - 10.2%；8.2%，CI = 4.3 - 12.1%，7.4%，CI = 4.8 - 9.9%）以及所有其他指标与30×30整群抽样调查的相似。LQAS设计的置信区间仅比30×30整群抽样调查的略宽；然而，LQAS设计所需的实施时间要少得多。
LQAS设计为耗时更长的30×30整群抽样调查提供了统计学上合适的替代方法。然而，需要使用独立样本而非嵌套研究设计进行额外的现场测试。
