Basics of Hydrogen/Methane Breath Testing
Hydrogen and methane are produced in the digestive system primarily only by the bacterial fermentation of carbohydrates (sugars, starches or vegetable fibers), so either of these gases appear in the expired air, it is usually a signal that carbohydrates or carbohydrate fragments have been exposed to bacteria, permitting such fermentation to take place2. The generation of H2 and/or CH4 will result in the reabsorption of some of these gases into the blood stream from the site of their digestion, and they will appear in the expired air.
Bacteria are ordinarily not present in significant numbers in the small intestine, where digestion and absorption of sugars take place. Therefore, when a challenge dose (eg. lactose) is ingested, the level of hydrogen in alveolar air will rise significantly within one to two hours (depending on the intestinal transit time) only if the sugar is not digested and, therefore reaches the colon.
The breath-H2 test is a simple non-invasive procedure which is readily accepted by patients and staff3, and which has greater reliability and acceptability than the blood test, according to most reports in the literature1,4-8. The lower dose of lactose usually does not cause the discomfort and explosive diarrhea frequently seen by malabsorbers who are given the large dose required for the blood test9.
A study with over 300 patients showed that G-I symptoms after a lactose challenge are strongly associated with the amount of H2 excreted, and the relationship between blood glucose change and symptom-severity was less evident.
False-positive breath-tests are rare, and when they occur they are usually caused by improperly doing the test - allowing the subject to smoke, to sleep or to eat shortly before or during the test11. Bacterial overgrowth (from the colon retrograde into the small intestine) can also produce a false-positive breath-test, but it is usually preceded by an elevated fasting breath-H2 level and the response is seen soon after the sugar is ingested (within 20-30 minutes).
The incidence of false-negative results with the breath-test is well below that seen with the blood test1,4,5. False-negative results are reported to be from 5-15% of all lactose malabsorbers,12-14 due to a variety of causes. Many of the false-negative reports can be avoided by measuring methane in addition to hydrogen15 because some methanogenic flora convert colonic H2 to CH4.
1. DiPalma, J.A.; Narvaez, R.M. Prediction of lactose malabsorption in referral patients. Dig Dis Sci. 1988; 33:303
2. Levitt, M.D. Production and excretion of hydrogen gas in man. New Engl. J. Med 1968; 281:122
3. Metz, G.; Jenkins, D.L.; Peters, T.J,; Newman, A.; Blendis, L.M. Breath hydrogen as a diagnostic method for hypolactasia. Lancet. 1975; 1(7917):1155-7
4. Davidson, G.P.; Robb, T.A.. Value of breath hydrogen analysis in management of diarrheal illness in childhood: Comparison with duodenal biopsy. J Ped Gastroenterol Nutr. 1985; 4:381-7
5. Fernandes, J.; Vos, C.E.; Douwes, A, C, ; Slotema, E.; Degenhart, H.J. Respiratory hydrogen excretion as a parameter for lactose malabsorption in children. Amer J Clin Nutr. 1978; 31:597-602
6. Newcomer, A.D.; McGill, D.B.; Thomas, R.J.; Hofmann, A.F. Prospective comparison of indirect methods for detecting lactase deficiency. New Engl J Med. 1975; 293:1232-6
7. Douwes, A.C.; Fernandes, J.; Degenhart H.J. Improved accuracy of lactose tolerance test in children, using expired H2 measurement. Arch Dis Child. 1978; 53:939-42
8. Solomons, N.W.; Garcia-Ibanez, R.; Viteri, F.E. Hydrogen breath test of lactose absorption in adults: The application of physiological doses and whole cow’s milk sources. Amer J Clin Nutr. 1980; 33:545-54
9. Jones, D.V.; Latham, M.C.; Kosikowski, F.V.; Woodward, G. Symptom response to lactosereduced milk in lactose-intolerant adults. Amer J Clin Nutr. 1976; 29(6):633-8
10. Hermans, M.M.; Brummer, R.J.; Ruijgers, A.M.; Stockbrugger, R.W. The relationship between lactose tolerance test results and symptoms of lactose intolerance. Am J Gastroenterol. 1997 (Jun); 92(6):981-4
11. Solomons, N.W. Evaluation of carbohydrate absorption: The hydrogen breath test in clinical practice. Clin Nutr J. 1984; 3:71-78
12. Filali, A.; Ben Hassine, L.; Dhouib, H.; Matri, S.; Ben Ammar, A.; Garoui, H. Study of malabsorption of lactose by the hydrogen breath test in a population of 70 Tunisian adults. Gastroenterol Clin Biol. 1987; 11:554-7
13. Douwes, A.C.; Schaap, C.; van der Kleivan Moorsel, J.M. Hydrogen breath test in school children. Arch Dis Child.1985; 60:333-7
14. Rogerro, P.; Offredi, M.L..; Mosca, F.; Perazzani, M.; Mangiaterra, V.; Ghislanzoni, P.; Marenghi, L.; Careddu, P. Lactose absorption and malabsorption in healthy Italian children: Do the quantity of malabsorbed sugar and the small bowel transit time play roles in symptom production? J Pediatr Gastroenterol Nutr.1985 (Feb); 4(1):82-614.
15. Cloarac, D.; Bornet, F.; Gouilloud, S.; Barry, J.Ll.; Salim, B.; Galmiche, J.P. Breath hydrogen response to lactulose in healthy subjects: relationship to methane producing status. Gut. 1990 (Mar); 31:300-4