OR值的全称是odd ratio, 又称比值比,对于发病率很低的疾病来说,它是OR值即是相对危险度的精确估计值。 计算公式如下: Odd ratio, 95% CI 假定我们要鉴别一个基因(或者标记位点SNP)有两个等位基因(等位):记为
odds 值在病例和对照可以计算如下: 病例Allele 1 Odds = A (A + B)/ B (A + B) =A/ B 对照Allele 1 Odds = C (C + D) / D (C + D) =C/ D 那么在这一点Allele 1的OR值可以计算如下: Odds Ratio =(A / B)/(C / D) =A D/B C 同样的,95% Confidence Intervals (CIs) 值可以计算如下: 95% CI of ln(OR) = ln(OR)±1.96(1/A +1/B +1/C +1/D)0.5 95% CI of OR = e95% CI of ln(OR)、 logistic回归中,OR值=1,表示该因素对疾病的发生不起作用 同时最好要算出它的95%CI OR为比值比,也称优势比 ln(OR)近似服从正态分布,因此在计算OR值置信区间的时候都是先计算ln(OR)置信区间,再计算OR置信区间(参考:http://www.ncbi.nlm./pmc/articles/PMC1127651/, http://bioterrorism./bt/products/bio_epi/scripts/mod12.pdf,http://www./faculty/gerstman/StatPrimer/case-control.pdf) 参考资料1(维基):http://en./wiki/Odds_ratio# 定义:Definition in terms of group-wise odds If the probabilities of the event in each of the groups arep1 (first group) and p2 (second group), then the odds ratio is: whereqx = 1 ? px. An odds ratio of 1 indicates that the condition or event under study is equally likely to occur in both groups. 参考资料2:http://www./snp-tools-excel/ 例子1: 例子2: http://www./specialarticles/jcn_10_268.pdf 参考资料4:http://intmedweb./ebmreviews/odds.html 参考资料5:http://hydra./scehsc/pdfs/D-1-3-3 lesson calculating odds.pdf参考资料6 :http:///class/gene210/files/writeups/gwas-howto-2.pdf 参考资料7: http://www./help/exact_tests_on_counts/gart.htm
(介绍了OR和RR区别和联系) |
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