Liu K, Stamler J, Stamler R, Cooper R, Shekelle R B, Schoenberger J A, Berkson D M, Lindberg H A, Marquardt J, Stevens E, Tokich T
J Chronic Dis. 1982;35(6):475-85. doi: 10.1016/0021-9681(82)90062-5.
Two methodological problems in characterizing an individual's plasma glucose level are examined in this study. First, how large is the intra-individual variation of an individual's 1-hr post-load glucose level and for this estimated intra-individual variation what are the probabilities of misclassifying individuals based on a one-time measurement only of glucose level? Second, do different tests-i.e. fasting, 1-hr, 2 hr post-load, GTT-yield consistent ranking for the same individual? The first of these was explored with data on subsamples from the Chicago Peoples Gas Company (PG) study and the Chicago Heart Association Detection Project in Industry (CHA) study; the second, with data from the Chicago Coronary Prevention Evaluation Program (CPEP). For both the PG and CHA studies, the estimated ratios of the intra- to inter-individual variances were generally higher for post-load plasma glucose than blood pressure, heart rate, weight and serum uric acid. The conditional probabilities of misclassifying individuals into quintiles or deciles based on one measurement of 1-hr post-load glucose were also estimated from these data. These estimated probabilities indicated that the possible attenuation due to intra-individual variation cannot abolish a strong association; however, it may create some problem if the relationship is not very strong. Furthermore, both rank correlation and quintile classification analyses show that fasting, 1-hr and 2-hr plasma glucose level characterize individuals differently. Thus it is possible that the inconsistent results of previous studies, all using a one-time measure of plasma glucose, are partially due to the large intra-individual variation of this variable, and the use of methods that are not highly consistent in their classification of individuals.
本研究探讨了表征个体血糖水平时的两个方法学问题。第一，个体负荷后1小时血糖水平的个体内变异有多大，对于这种估计的个体内变异，仅基于一次血糖水平测量将个体错误分类的概率是多少？第二，不同的测试——即空腹、负荷后1小时、2小时、葡萄糖耐量试验（GTT）——对同一个体是否产生一致的排序？第一个问题通过来自芝加哥人民煤气公司（PG）研究和芝加哥心脏协会工业检测项目（CHA）研究的子样本数据进行探究；第二个问题则通过芝加哥冠心病预防评估项目（CPEP）的数据进行研究。对于PG和CHA研究，负荷后血浆葡萄糖的个体内与个体间方差估计比率通常高于血压、心率、体重和血清尿酸。基于负荷后1小时血糖的一次测量将个体错误分类到五分位数或十分位数的条件概率也从这些数据中进行了估计。这些估计概率表明，个体内变异可能导致的衰减并不能消除强关联；然而，如果关系不是很强，可能会产生一些问题。此外，秩相关和五分位数分类分析均表明，空腹、负荷后1小时和2小时血浆葡萄糖水平对个体的表征有所不同。因此，以往所有使用一次性血浆葡萄糖测量的研究结果不一致，可能部分归因于该变量较大的个体内变异，以及在个体分类方法上缺乏高度一致性。
