Annals of Clinical Biochemistry > Volume 45, Number 1 > Pp. 50-58

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Original Article

Measurement of breath hydrogen and methane, together with lactase genotype, defines the current best practice for investigation of lactose sensitivity

Jonathan P Waud ¹, Stephanie B Matthews ¹ and Anthony K Campbell ² 

¹ Department of Medical Biochemistry and Immunology, Llandough Hospital, Cardiff and Vale NHS Trust, Llandough, Vale of Glamorgan, South Wales, Cardiff CF64 2XX; ² Department of Medical Biochemistry and Immunology, Cardiff University, Tenovus Building, Heath Park Campus, Heath Park, Cardiff CF14 4XN, UK

Corresponding author: Prof Anthony K Campbell. Email: campbellak{at}cf.ac.uk

Background: Currently, there is no ‘gold standard’ for detecting patients with sensitivity to lactose. Biochemical investigation by a breath hydrogen test alone detects <50% cases. Breath methane and symptoms are not recorded as standard practice. The clinical value of analysing C/T₁₃₉₁₀ and G/A₂₂₀₁₈ polymorphisms, strongly associated with lactose sensitivity, has not been established.

Methods: Two hundred and ten patients with unexplained gut and systemic symptoms and controls were challenged with 50 g lactose. Breath hydrogen and methane were measured and symptoms recorded. All were genotyped for two polymorphisms, C/T₁₃₉₁₀ and G/A₂₂₀₁₈.

Results: CC₁₃₉₁₀/GG₂₂₀₁₈ in 14.5%, CT₁₃₉₁₀/GA₂₂₀₁₈ in 39% and TT₁₃₉₁₀/AA₂₂₀₁₈ in 46.5%. One hundred percent of CC₁₃₉₁₀/GG₂₂₀₁₈ were lactose sensitive having a breath hydrogen >20 ppm within 6 h and symptoms. But the breath hydrogen test lacked sensitivity and specificity in the other groups. There was elevated breath hydrogen in 21% of CT₁₃₉₁₀/GA₂₂₀₁₈ and 15% of TT₁₃₉₁₀/AA₂₂₀₁₈ by 6 h, whereas 17 and 30.9% had elevated breath methane alone. Breath methane and breath hydrogen with clinical symptoms improved sensitivity and specificity, increasing detection of lactose sensitivity in genotypes CT/GA and TT/AA from <50 to >75%.

Conclusions: The data presented define the current best practice for the clinical identification of lactose sensitivity. Patients were first genotyped. Those identified as CC with symptoms should immediately undertake a 12-week lactose-free diet. Those identified as CT or TT should undertake a breath hydrogen and methane test. Those positive for hydrogen or methane along with symptoms or with symptoms only, should also undertake a lactose-free diet. Those with high hydrogen without symptoms should be investigated for causes other than lactose sensitivity.

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