Szilagyi Andrew, Malolepszy Paula, Hamard Elise, Xue Xiaoqing, Hilzenrat Nir, Ponniah Mary, MacNamara Elizabeth, Chong George
Division of Gastroenterology, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec, Canada.
Clin Gastroenterol Hepatol. 2007 Feb;5(2):192-6. doi: 10.1016/j.cgh.2006.06.009. Epub 2006 Jul 28.
BACKGROUND & AIMS: There is a discrepancy in outcome between the lactose tolerance and breath hydrogen tests for lactose maldigestion. The availability of a validated genetic test for lactase polymorphism allows a reevaluation of these tests.
Thirty healthy adults participated in a 50-g lactose challenge test at a university clinic. Blood was drawn for genetic and timed blood glucose testing (2 hours), and breath hydrogen was measured (4.5 hours). Lactase genetic polymorphism was assessed by a real-time polymerase chain reaction assay. Participants completed a diet questionnaire, and symptoms were recorded during the lactose challenge. Sensitivity and specificity were calculated for each indirect test. The 2-way kappa coefficient between these tests was evaluated. Student t test and Wilcoxon rank sum test were used to compare variables.
The lactose tolerance test as a standard had an 87.5% sensitivity and 92.7% specificity for genetic status. Only a moderate agreement between lactose tolerance test and breath hydrogen test was observed (2-way kappa coefficient, .53; 95% confidence interval, .22-.83). When genetic status was used as standard, symptoms had a moderate sensitivity and specificity. Lactose tolerance test had very good sensitivity, and the breath test had excellent specificity.
Both indirect tests independently have good to very good sensitivities and specificities for genetic lactase status. The noted disagreement likely reflects variables that affect the tests independently of intestinal lactase status. The value of these tests in the light of the availability of genetic testing is discussed.
乳糖消化不良的乳糖耐量试验和呼气氢试验结果存在差异。乳糖酶基因多态性有效基因检测方法的出现使得对这些试验需重新评估。
30名健康成年人在大学诊所参加了50克乳糖激发试验。采集血液用于基因检测和定时血糖检测（2小时），并测量呼气氢（4.5小时）。通过实时聚合酶链反应分析评估乳糖酶基因多态性。参与者完成饮食问卷，并在乳糖激发试验期间记录症状。计算每个间接试验的敏感性和特异性。评估这些试验之间的双向kappa系数。采用学生t检验和Wilcoxon秩和检验比较变量。
以乳糖耐量试验作为标准，其对基因状态的敏感性为87.5%，特异性为92.7%。乳糖耐量试验和呼气氢试验之间仅观察到中度一致性（双向kappa系数，0.53；95%置信区间，0.22 - 0.83）。以基因状态作为标准时，症状具有中度敏感性和特异性。乳糖耐量试验具有非常好的敏感性，呼气试验具有极好的特异性。
两种间接试验对遗传性乳糖酶状态均独立具有良好至非常好的敏感性和特异性。所指出的不一致可能反映了独立于肠道乳糖酶状态而影响试验的变量。讨论了鉴于基因检测的可用性这些试验的价值。
