Send at room temperature. Do not freeze or separate specimen.
Adult-type hypolactasia post weaning is an inherited condition, common especially in non-caucasians. Single nucleotide polymorphism genetic traits located upstream of the lactase coding region have been found to correlate with degree of lactase persistence. This genetic test is to look for presence of one of these polymorphisms. One should note that other than adult-type hypolactasia , lactase can also be lost from secondary intestinal causes e.g. Crohns or coeliac disease, gut infection or thyroid/sex hormonal imbalances. Congenital complete loss of lactase is very rare.
Biochemical methods to assess lactose malabsorption include breath hydrogen and methane test and direct disaccharidases assay on small intestinal mucosal biopsies. Lactose tolerance test with testing of serial plasma glucose response to lactose loading is no longer recommended.
The current best practice for investigation of lactose sensitivity involves combination use of lactase genotyping and hydrogen / methane breath test. Interpreting these laboratory findings in light of history, symptomatology and response to lactose-free diet trial help to ascertain if lactose intolerance is the diagnosis for the patient?s presentation.
References:
Mathews SB et al Systemic lactose intolerance: a new perspective on an old problem. Postgrad Med 2005; 81:167-173
Waud JP et al. Measurement of breath hydrogen and methane, together with lactase genotype, defines the current best practice for investigation of lactose sensitivity. Ann Clin Biochem 2008; 45:50-58
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