Zapata Carlos
Departamento de Genética, Universidad de Santiago, Santiago de Compostela, Spain.
Hum Hered. 2011;71(3):186-95. doi: 10.1159/000327732. Epub 2011 Jul 20.
BACKGROUND/OBJECTIVE: The analysis of linkage disequilibrium is relevant for the exploration of the structure and evolution of genomes and for the gene mapping of quantitative characters and human diseases. The strength of linkage disequilibrium between diallelic loci is commonly measured by the coefficients D' and r. Recent studies suggest that r is more useful than D' as a general measure of the strength of disequilibrium because it provides much more precise (lower sampling variance) and accurate (lower bias) estimates of disequilibrium. We compared for the first time the statistical properties of D' and r taking into account their differences in range.
The sampling properties of D' and r were evaluated by simulation under a variety of realistic population conditions and varying sample sizes using standardised statistics that allow for comparisons of the precision, accuracy and efficiency of estimates with different ranges.
Simulations revealed that estimates of r do not tend to be significantly more precise, accurate or efficient than those of D' when compared by means of standardised statistics.
The supposed advantage of r over D' based on direct comparisons of their sampling distributions is more apparent than real. The obtained results are useful to assess the uses and applications of these widely used disequilibrium measures.
背景/目的：连锁不平衡分析对于探索基因组的结构和进化以及对数量性状和人类疾病进行基因定位具有重要意义。双等位基因位点之间连锁不平衡的强度通常用系数D'和r来衡量。最近的研究表明，作为不平衡强度的一般度量，r比D'更有用，因为它能提供更精确（更低抽样方差）和准确（更低偏差）的不平衡估计。我们首次考虑了D'和r在范围上的差异，比较了它们的统计特性。
在各种现实的群体条件和不同样本量下，通过模拟使用标准化统计量来评估D'和r的抽样特性，这些统计量允许对不同范围估计的精度、准确性和效率进行比较。
模拟结果表明，通过标准化统计量进行比较时，r的估计在精度、准确性或效率方面并不比D'的估计显著更高。
基于对它们抽样分布的直接比较，r相对于D'的所谓优势更多是表面的而非实际的。所得结果对于评估这些广泛使用的不平衡度量的用途和应用很有帮助。
