Di Stefano M, Terulla V, Tana P, Mazzocchi S, Romero E, Corazza G R
1st Department of Internal Medicine, University of Pavia, Foundation IRCCS San Matteo Hospital, Pavia, Italy.
Dig Liver Dis. 2009 Jul;41(7):474-9. doi: 10.1016/j.dld.2008.09.020. Epub 2008 Nov 14.
Adult-type hypolactasia is a widespread condition throughout the world, causing lactose malabsorption. The lactose breath test is a simple tool for diagnosis but the need for prolonged monitoring of hydrogen excretion has led to a genetic test proposal. The aim of this study was to compare the genetic test with the lactose breath test in order to give some insights into the clinical value of genetic testing.
Thirty-two consecutive functional patients underwent lactose breath test and lactase genetic polymorphism analysis (C/T 13910 and G/A 22018). Intolerance symptoms after lactose load were also monitored.
All patients with positive lactose breath test showed homozygosis for both polymorphisms. Among the nine patients with a negative breath test result, six showed heterozygosis while three showed homozygosis. Intolerance symptoms were present in 16 homozygotic patients but also in one heterozygotic patient. The k value for the agreement between the genetic test and the lactose breath test was 0.74.
A positive genetic test for lactase non-persistence indicates whether lactase activity decline may represent a clinical problem for the patient, but does not give information on actual patient symptoms. On the contrary, this information is already available by combining the lactose breath test with intolerance symptom evaluation. Lactose absorption phenotype may be not yet evident until young adult age.
成人型低乳糖酶症在全球广泛存在，可导致乳糖吸收不良。乳糖呼气试验是一种简单的诊断工具，但由于需要长时间监测氢气排泄，因此有人提出进行基因检测。本研究的目的是比较基因检测与乳糖呼气试验，以便深入了解基因检测的临床价值。
对32例连续的功能性患者进行乳糖呼气试验和乳糖酶基因多态性分析（C/T 13910和G/A 22018）。还监测了乳糖负荷后的不耐受症状。
所有乳糖呼气试验阳性的患者在两种多态性上均显示纯合子。在9例呼气试验结果为阴性的患者中，6例显示杂合子，3例显示纯合子。16例纯合子患者出现不耐受症状，但1例杂合子患者也出现了不耐受症状。基因检测与乳糖呼气试验之间的一致性k值为0.74。
乳糖酶持续性缺乏的基因检测呈阳性表明乳糖酶活性下降是否可能对患者构成临床问题，但无法提供患者实际症状的信息。相反，通过将乳糖呼气试验与不耐受症状评估相结合，已经可以获得这些信息。乳糖吸收表型在青年期之前可能尚不明显。
