Rosado J L, Solomons N W
Clin Chem. 1983 Mar;29(3):545-8.
We examined the changes in sensitivity and specificity that would occur with alterations in the sample-collection schedule and (or) cutoff criterion for the increase in hydrogen concentration in breath after administration of doses of lactose in the dietary range. In a breath-analysis test to classify individuals as lactose-absorbers or lactose-malabsorbers, 41 subjects drank 360 mL of intact cow's milk, containing 18 g of lactose, and breath samples were collected and analyzed at 30-min intervals for 5 h. An increase in H2 concentration of greater than or equal to 20 microL/L above basal values at any of the 10 intervals was diagnostic of malabsorption. Increases of greater than or equal to 18 or greater than or equal to 15 microL/L were only 85% as specific in classifying the same individuals. Reduction in the number of samples tested per subject uniformly reduced the sensitivity. However, a simplified procedure suitable for field studies (in which four samples--at 0, 2, 3, and 4 h--are collected and analyzed with greater than or equal to 20 microL/L as the cutoff value) gives 80% sensitivity and 100% specificity, as compared with the 11-sample procedure.
我们研究了在饮食范围内给予不同剂量乳糖后，呼气中氢气浓度增加的样本采集时间表和（或）临界标准改变时，敏感性和特异性的变化情况。在一项用于将个体分类为乳糖吸收者或乳糖吸收不良者的呼气分析测试中，41名受试者饮用了360毫升含有18克乳糖的全脂牛奶，每隔30分钟采集一次呼气样本，并持续5小时进行分析。在10个时间间隔中的任何一个时间点，氢气浓度较基础值增加大于或等于20微升/升可诊断为吸收不良。增加大于或等于18微升/升或大于或等于15微升/升在对相同个体进行分类时特异性仅为85%。每个受试者测试样本数量的减少一致地降低了敏感性。然而，一种适用于现场研究的简化程序（在0、2、3和4小时采集并分析四个样本，以大于或等于20微升/升作为临界值）与11个样本的程序相比，敏感性为80%，特异性为100%。
