title: Primary hypolactasia diagnosis: Comparison between the gaxilose test, shortened lactose tolerance test, and clinical parameters corresponding to the C/T-13910 polymorphism.
abstract: There is no consensus on the most accurate method to diagnose primary hypolactasia. We aimed to compare the diagnostic accuracy of the new gaxilose test with 2 traditional tests (lactose tolerance test and clinical criteria) for the diagnosis of primary hypolactasia using the C/T-13910 polymorphism as a reference standard.
  
  
  
  Patients with a clinical suspicion of lactose intolerance were subjected to gaxilose tests, shortened lactose tolerance tests, and symptom questionnaires before and after overload with 50 g lactose and after a lactose-free diet. The diagnostic accuracy and degree of agreement and correlation were assessed using a genetic test (C/T-13910 polymorphism) as a reference standard and their respective 95% confidence intervals.
  
  
  
  Thirty consecutive patients (70% women) participated in the study. The genetic test confirmed the C/T-13910 polymorphism in 11 patients (36.8%). The presence of diarrhoea and the symptom score after lactose overload, along with the tolerance test, were the variables with the highest degree of agreement (κ > 0.60). Area under the ROC curve was >0.82 (p < 0.05), with sensitivity and specificity values of >0.80. However, the gaxilose test obtained lower values: κ, 0.47; area under curve, 0.75 (0.57-0.94); sensitivity, 0.82 (0.55-1); and specificity, 0.68 (0.45-0.92). The multivariate analysis showed an association between the post-overload symptom questionnaire and the results of the genetic test (odds ratio: 1.17; 1.04-1.31; p < 0.01).
  
  
  
  The presence of diarrhoea and the symptom score after overload with 50 g lactose showed a higher degree of agreement and diagnostic accuracy for primary hypolactasia than the gaxilose test when the genetic test is used as a reference standard.
authors: Department of Gastroenterology and Hepatology, Alto Guadalquivir Healthcare Agency, Alto Guadalquivir Hospital, Andújar, Jaén, Spain. Electronic address: jldominguez@ephag.es.
authors: José Luis
authors: JL
authors: Domínguez Jiménez
authors: Department of Biotechnology, Alto Guadalquivir Healthcare Agency, Alto Guadalquivir Hospital, Andújar, Jaén, Spain.
authors: Antonio
authors: A
authors: Fernández Suárez
authors: Department of Biotechnology, Alto Guadalquivir Healthcare Agency, Alto Guadalquivir Hospital, Andújar, Jaén, Spain.
authors: Aurora Úrsula
authors: AÚ
authors: Muñoz Colmenero
authors: Department of Biotechnology, Alto Guadalquivir Healthcare Agency, Alto Guadalquivir Hospital, Andújar, Jaén, Spain.
authors: Daniel
authors: D
authors: Fatela Cantillo
authors: Department of Biotechnology, U.G.C. Laboratory, Puerta del Mar Hospital, Cádiz, Spain.
authors: Iratxe
authors: I
authors: López Pelayo
mesh_terms: D000328:Adult; D003124:Colorimetry; D004187:Disaccharides / Q000652:urine*; D005260:Female; D005820:Genetic Testing; D006801:Humans; D043322:Lactase / Q000172:deficiency* / Q000235:genetics; D007785:Lactose / Q000378:metabolism; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000235:genetics; D007789:Lactose Tolerance Test; D008297:Male; D008875:Middle Aged; D065228:Non-Randomized Controlled Trials as Topic; D020641:Polymorphism, Single Nucleotide; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D004187:Disaccharides; C073827:4-O-galactopyranosylxylose; D043322:Lactase; D007785:Lactose
keywords: Gaxilose test; Hypolactasia; Lactose intolerance diagnosis; Lactose malabsorption