Hydrogen breath test

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The hydrogen breath test or H 2 breath test is a less stressful medical diagnostic method for the detection of various syndromes of the gastrointestinal tract. It has been used since 1969 for abdominal complaints such as chronic diarrhea and chronic or recurring abdominal pain, e.g. B. with lactose intolerance and fructose malabsorption.

Test principle

The test is based on measuring the concentration of hydrogen (H 2 ) in the exhaled air, which is produced in humans by the bacterial decomposition of carbohydrates in the colon , absorbed into the blood and exhaled through the lungs. The amount of hydrogen exhaled depends on the amount of carbohydrates that enter the large intestine. This fact is used diagnostically: the test person receives a carbohydrate drink (e.g. lactose [milk sugar] or fructose [fruit sugar]). If the carbohydrates are not completely absorbed in the small intestine, some of them reach the large intestine after about an hour, where H 2 is formed, which can be detected in the breath. If the hydrogen increase after the test drink exceeds 20 ppm, then there is a significant increase.

Test execution

The determination of the exhaled air hydrogen concentration in the unit parts per million (ppm) is nowadays usually carried out with a small handheld device similar to an alcohol measuring device used by the police. After a maximum inhalation, everything that the patient can blow out of the lungs is blown into the device. The device then displays the hydrogen concentration in the exhaled air in ppm. What all tests have in common is that the basal value is first measured on the fasted test person, which should be close to 0 ppm because of the (mandatory) long fasting before the test. Then a carbohydrate dissolved in a glass of water is drunk and the exhaled hydrogen concentration is measured every 10 to 30 minutes for one to three hours.

In parallel to the course of the hydrogen concentration in the breath, the test pays attention to symptoms (gurgling, gas, cramps, pain, diarrhea, etc.), as these are also a sign that bacteria are metabolizing the carbohydrates.

There should be a few days between different tests so that it can be safely ruled out that the first carbohydrate consumed is still responsible for symptoms in the following test, because these can occur one or two days later and last for a long time. Only in the case of a negative glucose test (no hydrogen and no symptoms) and a corresponding medical history could a further test be carried out - possibly with a slightly higher uncertainty regarding the origin of the symptoms in the second test.

Test types

There are different types of tests to be distinguished:

  1. Malabsorption test (lactose, fructose sorbitol and other sugar alcohols)
  2. general malabsorption (xylose)
  3. Small intestine transit time ( lactulose )
  4. Small intestine overgrowth (glucose) test
  5. Small intestine overgrowth test (lactulose)
  • Tests (1) - (3) assume that the small intestine is free of bacteria and that hydrogen is only produced by colon bacteria. If the difference between the basal value and the maximum value measured after drinking is more than 20 ppm in tests (1) - (2), the result indicates malabsorption of the test substance.
  • Because lactulose always reaches the large intestine, as it is generally not absorbed in the small intestine, an increase in the hydrogen concentration can always be expected in test (3). The time then corresponds to the arrival of lactulose in the large intestine, i.e. the small intestine transit time. This test is therefore also suitable for determining “non-responders”, i.e. people who do not exhale hydrogen after ingesting critical disaccharides.
  • Wrong test results:
    • False positive tests: Since the small intestine transit time is usually between 90 and 150 minutes, hydrogen formation well before 90 minutes can indicate an overgrowth in the small intestine.
    • False negative tests: With "non-responders" there is no significant increase in hydrogen if the bacteria either do not metabolize the carbohydrate, do not produce hydrogen during metabolism or the hydrogen produced is metabolized by other bacteria.
  • Test (4) assumes that the glucose is absorbed so quickly in the small intestine that it never gets into the large intestine. An increase in hydrogen in the air we breathe therefore suggests a pathogenic colonization of the small intestine with bacteria. Since glucose is absorbed quickly, after 60 minutes it can no longer be expected that there will be any glucose in the intestine at all. However, glucose can be absorbed before it reaches the bacteria-populated area of ​​the small intestine - then the result is false negative.
  • In test (5) this option is switched off in comparison to test (4), since lactulose, because it is not resorbed, always reaches the point with the malocclusion in the small intestine in order to produce hydrogen there. Since lactulose always reaches the large intestine and thus always produces hydrogen after the small intestine transit time, the difficulty lies in distinguishing which hydrogen comes from the small intestine and which from the large intestine. Speak for a small intestine colonization:
    • significant amounts of hydrogen before 75 min
    • a two-peak course (e.g. an increase at 90 min, and then a further increase at 150 min; in this case the first peak can be assigned to an overgrowth of the small intestine and the second peak to the lactulose in the large intestine)
    • a high base value for hydrogen concentration.
  • According to Ledochowski, tests (4) or (5) indicate pathogenic bacterial colonization of the small intestine if the increase is more than 10 ppm hydrogen - if symptoms occur, an increase of only 5 ppm is sufficient.

Since the small intestine transit time varies greatly from person to person (40 healthy subjects: 30–120 min, mean 72 min; 8 healthy subjects: 38–136 min, mean 77 min), the interpretation of the test results is not always clear.

Parallel blood test

With the lactose breath test it is useful to also measure the blood sugar level (glucose) before and during the breath measurements. If there is maldigestion, the tested sugar is not broken down and absorbed, and the blood sugar level thus remains the same. If there is no maldigestion, the blood sugar level rises because the breakdown product of lactose, glucose, has been absorbed into the blood. Investigating changes in blood sugar levels is less sensitive and also more complex than the breath test. The blood test is helpful if there is a suspicion of “non-responders”.

In the intestine, fructose is not converted into glucose, but rather delayed and very slowly in the liver, so that any fluctuations in the blood sugar level that may be caused by it are minimal and not meaningful. Macdonald (1978) investigated the temporal change of 8 blood serum values ​​(glucose = blood sugar, insulin, fructose, triglycerides, lactate, pyruvate, glycerine and uric acid) after oral administration of various amounts of fructose (0.25, 0.5, 0 , 75 and 1 g fructose per kg body weight). He showed that the fructose concentration alone increases proportionally to the amount administered. Truswell (1988) showed in 103 people that the change in fructose concentration does not correlate with malabsorption - contrary to expectations, the fructose serum concentration in malabsorbers tended to rise even more sharply than in healthy test persons. A blood test is therefore not useful to obtain information about fructose malabsorption.

backgrounds

In the case of lactose intolerance , the small intestine lacks sufficient production of the enzyme lactase , which is more common in northern Europeans , which splits the milk sugar molecules into the components glucose and galactose . This is why lactose reaches the large intestine, where it is metabolized by certain intestinal bacteria. This produces short-chain fatty acids and gases, including hydrogen (H 2 ), which can be measured with the H 2 breath test.

In the case of fructose malabsorption , the transport protein GLUT 5, which is required for the absorption of the fructose into the blood through the mucous membrane of the small intestine, is not available in sufficient quantity or quality. The fructose molecules that reach the large intestine are processed there in a similar way to lactose intolerance by intestinal bacteria, releasing hydrogen.

Dosage of the carbohydrates

For adults, the following quantities can be used as guidelines for the amount of carbohydrates to be taken:

Test carbohydrate amount Detectable syndrome / measurand
Lactose 50 g Lactose maldigestion / lactose intolerance
Fructose 20-25 g Fructose malabsorption
glucose 50-80 g Small intestine colonization (glucose does not get into the large intestine)
Lactulose 10 g Transit time from mouth to colon (lactulose is not absorbed)
Sorbitol 5-10 g Sorbitol malabsorption

The higher the amount of carbohydrate administered in the tolerance tests, the more likely malabsorption / maldigestion is.

Test preparation

In order to rule out that hydrogen is detected during the measurements, which does not come from the test substance, some precautions must be observed:

  • Before the breath test, nothing should be eaten for at least 14 hours and nothing should be drunk apart from pure tap water, so that all food residues and their bacterial decomposition in the colon are completely eliminated when the basal value is measured. This applies as early as 24 hours in advance to foods that are difficult to digest (onions, cabbage, beans, fiber, health food products, fruit) and of course to the laxative lactulose. These sugars must also be avoided for 24 hours before a lactose hydrogen breath test / fructose hydrogen breath test.
  • In order to achieve a basal value of 0 for meaningful test results, oral hygiene is important before the test, as bacteria in the oral cavity also produce hydrogen. 100% of the hydrogen produced in the oral cavity gets into the measuring device, but only 20% of that produced in the intestine (relevant for people with fixed braces). Since some doctors advise against brushing their teeth, Ledochowski writes that no negative effects of brushing their teeth could be determined in his patient collective in about 1000 patients. We recommend using a toothpaste that is as sorbitol-free as possible and then rinsing the mouth extremely thoroughly and avoiding swallowing the toothpaste.
  • Physical exertion during the tests must be avoided as it has a negative effect on the absorption of carbohydrates; proven by strong malabsorption by using ergometers during the fructose H2 breath test of non-malabsorbers.
  • Smoking before and during the H 2 breath test must also be avoided, as the carbon monoxide formed interferes with the detector of the hydrogen meter ( cross-sensitivity ).
  • A breath test shortly after taking antibiotics or after an intestinal lavage (in preparation for a colonoscopy) is worthless, as the test result is falsified by the expected influence on the intestinal flora.

Non-responders

In the case of people who harbor relevant populations of methane-producing bacteria in their colon flora, all of the hydrogen formed by other types of bacteria may be metabolized to methane , whereby the carbon dioxide that was also previously formed by bacteria is reduced. Despite the arrival of unabsorbed carbohydrates in the large intestine, it can happen that any hydrogen formed in the exhaled air cannot be detected. If, despite a negative hydrogen test, symptoms occur during or shortly after the examination, it makes sense to check for non-responder status using a lactulose breath test. In these cases it is advisable to repeat the test by measuring the methane content of the exhaled air.

In the Western European population, the proportion of people excreting methane is around 35%, with the majority of these people harboring the methane-forming bacteria mainly in the middle and descending part of the large intestine. In the cecum and the ascending part of the large intestine, the pH value is usually lower, so that the conditions here are unfavorable for methanogenesis. Therefore, the proportion of non-responders in whom the hydrogen produced is metabolized to methane in the appendix is significantly lower (approx. 5–10% of the population).

Individual evidence

  1. ^ MD Levitt: Production and excretion of hydrogen gas in man . In: The New England Journal of Medicine . 281, No. 5, 1969, pp. 122-127.
  2. ↑ JH Bond, MD Levitt: Use of Pulmonary Hydrogen (H 2 ) Measurements to Quantitate Carbohydrate Absorption . In: The Journal of Clinical Investigation . 51, No., 1972, pp. 1219-1225.
  3. ↑ a b c J.H. Bond, MD Levitt, R. Prentiss: Investigation of small bowel transit time in man utilizing pulmonary hydrogen (H 2 ) measurements . In: J. Lab. Clin. Med. . 85, No. 4, 1975, pp. 546-555.
  4. ↑ G. Barnes, W. McKellar, S. Lawrance: Detection of fructose malabsorption by breath hydrogen test in a child with diarrhea . In: The Journal of Pediatrics . 103, No. 4, 1975, pp. 575-577.
  5. ↑ a b c d e f g h i j M. Ledochowski: H2 breath tests . Ledochowski publishing house, 2008; ISBN 978-3-9502468-0-3 .
  6. ↑ a b c P. Born, J. Zeck, M. Stark, M. Classen, R. Lorenz: Sugar substitutes: comparative study on the intestinal absorption of fructose, sorbitol and xylitol . In: Medical Clinic . 89, No. 11, 1994, pp. 575-578.
  7. ↑ a b c d P. Born: Carbohydrate malabsorption - symptoms, diagnostics, therapy . In: Biological Medicine . 6, 1990, pp. 356-361.
  8. ↑ SD Ladas, C. Latoufis, H. Giannopoulou, J. Hatziioannou, SA Raptis: Reproducible Lactulose Hydrogen Breath Test as a Measure of Mouth-to-Cecum Transit Time . In: Digestive Diseases and Science . 34, No. 6, 1989, pp. 919-924.
  9. ^ HJ Wildgrube: Hydrogen (H 2 ) breath tests in the diagnosis of diseases of the small intestine . In: Z. Gastroenterology . 21, No. 11, 1983, pp. 628-636.
  10. ^ GC Cook: Absorption and metabolism of D (-) fructose in man . In: The American Journal of Clinical Nutrition . 24, 1971, pp. 1302-1307.
  11. ^ I. Macdonald, A. Keyser, D. Pacy: Some effects, in man, of varying the load of glucose, sucrose, fructose, or sorbitol on various metabolites in blood . (PDF) In: The American Journal of Clinical Nutrition . 31, 1978, pp. 1305-1311.
  12. ↑ AS Truswell, JM Seach, AW Thorburn: Incomplete absorption of pure fructose in healthy subjects and the Facilitating effect of glucose . (PDF) In: Am J Clin Nutr . 48, 1988, pp. 1424-1430.
  13. ↑ D. Paas: The lactose intolerance book . Verlag Monsenstein and Vannerdat, 2007, ISBN 978-3-86582-531-5 .
  14. ↑ T. Fujisawa, K. Mulligan, L. Schumacher, J. Riby, N. Kretchmer: The effect of exercise on fructose absorption . In: The American Journal of Clinical Nutrition . 58, 1993, pp. 75-79.
  15. ↑ Operating instructions for the Gastrolyzer H2 breath test device from Specialmed / Bedfont (PDF)
  16. ↑ T. Gilat, H. Ben Hur, E. Gelman-Malachi, R. Terdiman, Y. Peled: Alterations of the colonic flora and their effect on the hydrogen breath test . In: Good . 19, 1978, pp. 602-605.
  17. ↑ L. Nollet, W. Verstraete: Gastro-Enteric Methane Versus Sulphate and Volatile Fatty Acid Production . In: Environmental Monitoring and Assessment . 42, 1996, pp. 113-131.