Rollán Antonio, Vial Cecilia, Quesada Soledad, Espinoza Karena, Hatton Mary, Puga Alonso, Repetto Gabriela
Unidad de Gastroenterología, Departamento de Medicina, Facultad de Medicina, Universidad del Desarrollo-Clínica Alemana, Santiago, Chile.
Rev Med Chil. 2012 Sep;140(9):1101-8. doi: 10.4067/S0034-98872012000900001.
Genetically programmed adult-type hypolactasia affects 56% of Chilean population. Ideally, diagnosis should be confirmed.
To compare diagnostic yield of genetic test, hydrogen (H2) expiratory test and a validated symptomatic structured survey (SS).
Patients submitted to H2 test answered a historic (anamnestic) and current SS (after the ingestion of 25 g of lactose). A blood sample was obtained for determination of genetic polymorphisms C/T_13910, C/G_13907 and G/A_22018 by polymerase chain reaction. The gold standard for diagnosis of lactose intolerance (LI) was the agreement of at least two of three tests.
Sixty-one participants aged 39 ± 12 years (21 males), were studied. Anamnestic SS was diagnostic of LI in all cases (score > 7), while current SS detected LI in 27/61 (46%). H2 test (an increase > 15 ppm after ingestion of 25 g of lactose) showed LI in 31/61 (51%). The locus C/G_13907 showed no polymorphism and locus G/A_22018 was in complete linkage disequilibrium with C/T_13910. Genotype C/C_13910, associated to hypolactasia, was present in 30/58 (52%). According to the gold-standard, 32/61 (52.5%) patients were diagnosed as LI. Sensitivity and specificity were, respectively, 79% and 69% for current SS, 93% and 93% for H2 test and 97% and 93% for the genetic test. The last two showed a positive likelihood ratio (LR) > 10 and a negative LR < 0.1, figures within the range considered clinically useful.
Genotype C/C_13910 is responsible for hypolactasia in this population. Anamnestic report of symptoms after milk ingestion and symptoms after lactose ingestion, are not accurate enough. H2 and genetic tests are simple and similarly accurate to diagnose lactose intolerance in adults.
基因编程导致的成人型乳糖酶缺乏症影响着56%的智利人口。理想情况下，诊断应得到确认。
比较基因检测、呼气氢（H2）试验和经过验证的症状性结构化调查（SS）的诊断效能。
接受H2试验的患者回答一份病史（回忆性）和当前的SS（摄入25克乳糖后）。采集血样，通过聚合酶链反应测定基因多态性C/T_13910、C/G_13907和G/A_22018。乳糖不耐受（LI）诊断的金标准是三项检测中至少两项结果一致。
研究了61名年龄39±12岁的参与者（21名男性）。回忆性SS在所有病例中均诊断为LI（评分>7），而当前SS在27/61（46%）的病例中检测到LI。H2试验（摄入25克乳糖后增加>15 ppm）在31/61（51%）的病例中显示为LI。C/G_13907位点未显示多态性，G/A_22018位点与C/T_13910完全连锁不平衡。与乳糖酶缺乏相关的C/C_13910基因型在30/58（52%）的病例中存在。根据金标准，32/61（52.5%）的患者被诊断为LI。当前SS的敏感性和特异性分别为79%和69%，H2试验为93%和93%，基因检测为97%和93%。后两者显示阳性似然比（LR）>10，阴性似然比<0.1，这些数值在临床有用范围内。
C/C_13910基因型是该人群乳糖酶缺乏的原因。摄入牛奶后症状的回忆性报告和摄入乳糖后症状的报告不够准确。H2试验和基因检测简单且在诊断成人乳糖不耐受方面准确性相似。
