Urea breath test

• • Expired air is collected after ingestion of 13C-labelled urea.

• • If H. pylori present, bacterial urease breaks down urea → ammonium and bicarbonate, then → CO2 and ammonia.

• • Expired 13CO2 is collected into a tube 30min after ingestion, measured by a mass spectrophotometer, and compared with one collected prior to ingestion.

• • Test almost 100% sensitive and specific, and remains the gold standard to confirm eradication.

Drew Provan. (2018). Oxford Handbook of Clinical and Laboratory Investigation. 4th ed. Oxford University Press.

Hydrogen breath tests

Rationale

In mammals, the only source of breath hydrogen is bacterial fermentation of carbohydrates. Hydrogen is absorbed from the intestinal lumen and expired during breathing. In bacterial overgrowth, hydrogen production can occur in the small intestine, as well as in the colon.

Method

• • A mouthwash is given beforehand to reduce contamination by oral bacteria.

• • Test dose of glucose/lactose (50g of either) or lactulose (10–15mL) and breath hydrogen measured.

• • An early peak (e.g. 40min) suggests bacterial overgrowth.

• • This test can be used for other short-chain carbohydrates, such as fructose or lactose, or lactulose, to determine if your child is malabsorbing one or more sugars, or if there are signs of bacterial overgrowth.

  Currently hydrogen breath tests are being performed at Alder Hey Children’s Hospital upon referral from your GP (or Paediatrician if resident in North Wales).