European Review for Medical and Pharmacological Sciences 2013; 17(Suppl 2): -90-98 Tricks for interpreting and making a good report on hydrogen and 13C breath tests G. D’ANGELO, T.A. DI RIENZO, F. SCALDAFERRI, F. DEL ZOMPO, M. PIZZOFERRATO, L.R. LOPETUSO, L. LATERZA, G. BRUNO, V. PETITO, M.C. CAMPANALE, V. CESARIO, F. FRANCESCHI, G. CAMMAROTA, E. GAETANI, A. GASBARRINI, V. OJETTI Department of Internal Medicine, Gastroenterology Division, School of Medicine Catholic University of the Sacred Hearth, Rome, Italy Abstract. Breath tests (BT) represent a valid Introduction and non-invasive diagnostic tool in many gas- troenterological disorders. Their wide diffusion Breath tests (BT) represent a valid and non-in- is due to the low cost, simplicity and repro- ducibility and their common indications include vasive diagnostic tool in many gastroenterological diagnosis of carbohydrate malabsorption, Heli- disorders. Hydrogen-breath tests are based on the cobacter pylori infection, small bowel bacterial fact that gases produced by colonic bacterial fer- overgrowth, gastric emptying time and orocae- mentation diffuses into the blood and are excreted cal transit time. in breath samples, where it can be easily quanti- The review deals with key points on method- fied. There is a growing interest in breath tests but ology, which would influence the correct inter- many differences persist in the methodology used. pretation of the test and on a correct report. While a clear guideline is available for lac- Hydrogen Breath test (HBT) has become an tose and glucose breath tests, no gold stan- important diagnostic tool in many Gastroentero- dard is available for Sorbitol, Fructose or other logical conditions, characterized by abdominal H2 BTs. pain, discomfort, bloating etc. Its wide diffusion Orocaecal transit time (OCTT) defined as is due to the low cost, simplicity and repro- time between assumption of 10 g lactulose and ducibility: it represents a valid and non-invasive a peak > 10 ppm over the baseline value, is a well-defined breath test. The possible value of test to diagnose carbohydrate malabsorption, lactulose as a diagnostic test for the diagnosis small bowel bacterial overgrowth, and for the de- of small bowel bacterial overgrowth is still un- termination of orocaecal transit time. der debate. 13C-breath tests use 13C-labelled substrates in Among 13C breath test, the best and well order to perform a safe non-invasive evaluation of characterized is represented by the urea breath several metabolic pathways. The turnover of the test. Well-defined protocols are available also 13 13 C-substrate throughout the specific explored for other C tests, although a reimbursement 13 for these tests is still not available. pathway is assessed by measuring CO2 in exhaled 13 Critical points in breath testing include the air. The availability of plenty of C-substrates patient preparation for test, type of substrate gives these tests a wide range of potential applica- utilized, reading machines, time between when tions, although the routine clinical use of certain the test is performed and when the test is substrates may be sometimes affected by their high processed. Another crucial point involves clini- costs. The most used 13C breath test is the one for cal conclusions coming from each test. For ex- Helicobacter pylori ample, even if lactulose could be utilized for di- diagnosing infection. agnosing small bowel bacterial overgrowth, In this paper we summarize key element on 13 this indication should be only secondary to assessing and interpreting H2 and major C orocaecal transit time, and added into notes, as breath tests, and we will provide a guide for an clinical guidelines are still uncertain. accurate breath test report. Key words: Tricks on hydrogen and methane excretion Hydrogen isn’t produced in healthy humans Breath test report, H2 breath test, C13 breath test. fasting and at rest, but it is only generated during 90 Corresponding Author: Veronica Ojetti MD, Ph.D; e-mail: [email protected] Tricks for interpreting and making a good report on hydrogen and 13C breath tests anaerobic metabolism, which occurs, for example, Tricks on sampling H2 from alveolar during bacterial fermentation. Anaerobic bacteria expirates for H2 breath testing metabolize sugar molecules, producing CO2, We can measure hydrogen concentrations in short-chain fatty acid (SCFA) and Hydrogen1. Un- end-expiratory breath samples using gas chro- absorbed carbohydrates are so fermented by matography or electrochemical cells. Stationary colonic bacteria and the hydrogen, like other gases dedicated gas chromatographs represent the gold produced within the intestine, is absorbed through standard for hydrogen determinations in breath, as the intestinal wall, passes in the blood circulation, they were previously validated in comparison with reaches the lungs, and finally it is released and ex- non-dedicated instruments in terms of linearity and haled in the breath samples. The amount of hydro- reproducibility of results10-12. Stationary dedicated gen produced by carbohydrate fermentation varies gas-chromatographs could be made with solid state according to the individual’s microbiota, as hydro- sensors, and they represent the gold standard for gen is also used by bacteria for other metabolic hydrogen determination, or with electrochemical processes, including conversion to methane. sensor, which also show a good accuracy, although In fasting state, normal hydrogen baseline val- they will undergo to a natural “drift” over time. ues are reported to be 7 ± 5 ppm2, if it results too Gas measurement must be performed in alveolar high (>10-16 ppm), breath test shouldn’t be per- air, avoiding the interference represented by respira- formed3. The ingestion of rice flour and meat is tory dead space air. The three systems are available not associated with a detectable increase in breath to collect alveolar air: the modified Haldan-Priestley hydrogen excretion, so they are eaten the evening tube, the Y-Piece device and the two bag-system13. before the test4,5. In response to the test, some peo- The most efficient method to remove dead space air ple produce huge amount of hydrogen in response and guarantee complete respiratory exchanges is to to sugars, some produce lower amounts, and about inhale maximally, hold the inhalation for 15 s and 15% produce apparently none (designated ‘non- expire into the bag14. It could be also considered as a hydrogen producers’), as the expired hydrogen marker of correct sampling the concentration of throughout the test dose not reach the limit detec- CO2, which levels in alveolar air are stable around tion rate. In some case of apparent hydrogen non 5-5.5%:, it is possible to reduce variability due to the production, methane determination could repre- death space, measuring CO2 in breath sample and 15 sent a valid alternative, although insufficient data correcting for the ideal value of CO2 . are presented in this topic. In patients that do not Breath samples are currently stored in plastic produce methane neither hydrogen (a condition syringes, an inexpensive method allowing the present in about 5% of the population), there is no analysis of gases with no further handling. Be- indication of performing breath tests6 and no indi- cause of the high diffusion capacity of hydrogen, cation exists on whether increase test time would samples should be analyzed as soon as possible, exert any role. This condition is mainly due to a avoiding storage longer than 12 h; however, sim- different intestinal flora composition, which in ple refrigeration of plastic syringes is sufficient turn is influenced by many factors including age, to ensure the stability of hydrogen concentrations susceptibility to infections, dietary habits, im- for a long time. At room temperature, after 5 munological factors, intraluminal pH, interaction days, the hydrogen concentration is reduced up among components of intestinal flora and fer- to 30%, while at –20 °C the reduction is equal to mentable substrates, recent antibiotic therapy, use 5% and only 7% after 15 days. Moreover, at –20 of laxatives (preparation for colonoscopy), or for °C no hydrogen loss is detectable for 2 days13. the predominance of methane producing bacteria Hydrogen concentration in breath samples must, in the colon7-9. Some groups try to overcome this therefore, be determined within 6 h of sampling. problem by testing initially lactulose: this synthet- ic disaccharide cannot be absorbed in humans and Tricks on Lactose breath test is, therefore, always fermented producing hydro- interpretation gen, except for the “non-H2-producer”. It is, there- Lactose breath test shows good sensitivity fore, conceivable that a slow gastrointestinal tran- (mean value of 77.5%) and excellent specificity sit of the substrate may be responsible for false (mean value of 97.6%) for lactose intolerance in negative results. It was shown that the prolonga- patients which display or not symptoms16, 17. False tion of measurement from 2 to 4 hours induce a negative tests, however, can be due to “hydrogen significant reduction of the prevalence of “H2 non non-producers”; false positive breath tests are less producer”8. frequent and are mainly secondary to of small 91 G. D’Angelo, T.A. Di Rienzo, F. Scaldaferri, F. Del Zompo et al bowel bacterial overgrowth. LBT was considered colon, so it is a suitable substrate to detect proxi- positive when the peak of hydrogen was 20 ppm mal small bowel overgrowth. A rise in H2, after over the baseline. In children some laboratories the assumption of the substrate, means that glu- have used > 10 ppm as cutoff value, but a rise of > cose meets bacteria in the small bowel, before its 20 ppm over baseline correlates better with symp- absorption. Because of its early absorption, GBT tom development18. may not able to diagnose SIBO of the distal If the value rises more than 10 ppm but less small intestine (ileum). Sensitivity and specifici- than 20 ppm above the base value, the test could ty are 62.5% and 77.8 %, respectively compared be considered as “borderline”19.