Serum diamine oxidase activity is associated with lactose malabsorption phenotypic variation

Objectives: Recently, an intermediate lactose intolerance (LI) phenotype based on the lactase gene (LCT) C/T_ 1391 0 polymorphism was proposed. However, a multifactorial genesis of LI phenotypic variation including endogenous and exogenous factors cannot be ruled out Therefore, this study was conducted to investigate a possible association between serum diamine oxidase (DAD) and LI phenotypes in individuals with lactose malabsorption (LM). Design and methods: A total of 121 ambulatory patients with LM were included in this retrospective study. The lactose, hydrogen breath test (LIBT) and serum DAO activity measurements were performed on the same day. A thorough anamnesis with respect to gastrointestinal symptoms was carried out at the initial consultation. Results: In total, 44 (36.4%) patients with a serum DAO activity <10 U/mL showed higher H-2 levels after 60 (mean: 53.7 +/- 57.6 vs 34.5 +/- 31;7 parts per million [ppm], p = 0.116), 90 (mean: 70.3 +/- 57.5 vs 52.7 +/- 41.4 ppm, p = 0.184) and 120 min (mean: 98.9 +/- 72.5 vs 67.9 +/- 44.9 ppm, p = 0.012) during LHBT compared to 77 (63.6%) patients with a serum DAO activity U/mL. Individuals with a serum DAO activity <10 U/mL tended to report gastrointestinal symptoms during the LHBT more often (p = 0.091). Conclusions: Our findings suggest that patients with LM and a serum DAD activity level < 10 U/mL had higher end-expiratory H-2 levels and tended to be more symptomatic during the LHBT compared to LM patients with DAD activity levels >= 10 U/mL (C) 2016 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.