Hydrogen breath test for the diagnosis of lactose intolerance, is the routine sugar load the best one？

AIM： To evaluate the prevalence of lactose intolerance （LI） following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test （HBT）-25. METHODS： Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g. Peak hydrogen production, area under the curve of hydrogen excretion and occurrence of symptoms were recorded. RESULTS： Only 16 patients （17.77%） with positive HBT-25 proved positive at HBT-12.5. Hydrogen production was lower as compared to HBT-25 （peak value 21.55 parts per million （ppm） ± 29.54 SD vs 99.43 ppm ± 40.01 SD; P 〈 0.001）. Symptoms were present in only 13 patients. The absence of symptoms during the high-dose test has a high negative predictive value （0.84） for a negative low-dose test. The presence of symptoms during the first test was not useful for predicting a positive low-dose test （positive predictive value 0.06-0.31）. CONCLUSION： Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a ＂standard＂ HBT is, in most instances, unnecessary. Thus, the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI, and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance.     

Clinical applicability of shortenedd-Xylose breath test for diagnosis of intestinal malabsorption

Urinary and/or plasmaticd-xylose tests are broadly used in clinical practice for the diagnosis of intestinal malabsorption. A 5-hr hydrogen breath test (H₂ BT) has also proven useful. Our goal was to determine whether a shorter, hence more efficient, 3-hr test would perform as well as the 5-hr test. We studied 33 patients with proven malabsorption, 44 patients with irritable bowel syndrome (IBS), and 27 healthy subjects. Each individual ingested 25 g ofd-xylose, and alveolar breath samples were obtained thereafter at 30 min intervals for 5 hr. Breath samples were analyzed for H₂ by gas chromatography. Individual peak delta changes and area under the curve (AUC) were calculated. Simultaneously, the 5-hr cumulative urinary excretion ofd-xylose was measured by colorimetry. Results of 5-hr tests were compared with those of the first 3 hrs. In the malabsorption group, the 5-hr test showed a markedly enhanced production of H₂ relative to healthy controls (delta: 60.7±6.4 vs 7.7±1.5 and AUC: 8465.0±985.4 vs 393.2±232.6,P<0.001 for both) and a reduced urinary excretion ofd-xylose (2.8±0.3 g/5 hr vs 6.3±0.2,P<0.001). Results in IBS patients did not differ from those in healthy controls. Three-hour analysis also reflected an enhanced production of H₂ in the malabsorption group (delta: 45.4±6.4 and AUC: 3700.0±545.6,P<0.001 vs healthy controls). Correlation between 3-hr and 5-hr tests was significant in healthy controls (r=0.9), IBS (r=0.9), and malabsorption (r=0.8). The sensitivity of the 3-hr test was lower than of the 5-hr test (0.72 vs 0.91). The loss of sensitivity of the 3-hr test was attributed to a delayed appearance of the delta peak in the malabsorption group. In conclusion, the H₂ breath test withd-xylose is a useful test for the diagnosis of the intestinal malabsorption, but requires a 5-hr monitoring period to be reliable.     

Lactose malabsorption, irritable bowel syndrome and self-reported milk intolerance

BACKGROUND: The relationship between lactose malabsorption, irritable bowel syndrome and development of intestinal symptoms is unclear, especially when the ingested dose of milk is small. Thus, the role of hydrogen breath testing in the diagnostic work-up of patients with nonspecific intestinal symptoms is still debated. AIMS: To establish the relationship between lactose malabsorption, severe self-reported milk intolerance, irritable bowel syndrome and related symptoms. METHODS: The prevalence of lactose malabsorption was prospectively assessed by means of a hydrogen breath test in 839 patients (503 with irritable bowel syndrome, based on the Rome criteria, regularly consuming milk, and 336 subjects who identified themself as milk intolerant, after an oral load of 25 g lactose). The test was considered "positive" when a hydrogen peak exceeding 20 ppm over baseline values was observed in two or more samples. Attempts were also made to establish whether the predominant presenting symptom (diarrhoea, constipation, alternating diarrhoea and constipation, pain and gaseousness) might be helpful in predicting the outcome of the breath test. RESULTS: The prevalence of a positive breath test was comparable in the two groups (337 patients with irritable bowel syndrome (66.9%) vs 240 patients with milk intolerance (71.4%)). The same holds true for the first peak of hydrogen excretion, total hydrogen output and prevalence of symptoms during, and in the four hours after, the test. The predominant presenting symptom was not useful for predicting outcome of the test either in regular milk users or in milk intolerant subjects. CONCLUSIONS: The almost identical results of the lactose breath test of patients with irritable bowel syndrome and subjects with self-reported milk intolerance suggests that the two conditions overlap to such an extent that the clinical approach should be the same. A lactose breath test should always be included in the diagnostic work-up for irritable bowel syndrome, as fermentation of malabsorbed lactose is likely responsible for triggering symptoms. Conversely, lactase deficiency is probably irrelevant in most subjects not affected by irritable bowel syndrome, within a moderate milk consumption.     

Carbohydrate Malabsorption Syndromes and Early Signs of Mental Depression in Females

Fructose and lactose malabsorption are characterized by impaired duodenal fructose transport or by the deficiency of mucosal lactase, respectively. As a consequence, the nonabsorbed saccharides reach the colon, where they are broken down by bacteria to short fatty acids, CO₂, and H₂. Bloating, cramps, osmotic diarrhea, and other symptoms of irritable bowel syndrome are the consequence and can be seen in about 50% of carbohydrate malabsorbers. We have previously shown that fructose as well as lactose malabsorption were associated with signs of mental depression. It was therefore of interest to investigate possible interactions between fructose and lactose malabsorption and their influence on the development of signs of depression. In all, 111 otherwise healthy volunteers (81 females and 30 males) with gastrointestinal complaints were analyzed by measuring breath H₂ concentrations after an oral dose of 50 g lactose and of 50 g fructose one week apart. They were classified as normals, isolated fructose malabsorbers, isolated lactose malabsorbers, and combined fructose/lactose malabsorbers. All patients filled out a Becks depression inventory–questionnaire. Twenty-five individuals (22.5%) were neither fructose nor lactose malabsorbers (group 1), 69 (62.2%) were only fructose malabsorbers (group 2), 4 (3.6%) were only lactose malabsorbers (group 3), and 13 (11.7%) presented with fructose and lactose malabsorption together (group 4). Isolated fructose malabsorption and combined fructose/lactose malabsorption was significantly associated with a higher Becks depression score. Further analysis of the data show that this association was strong in females (P < 0.01), but there was no such association between carbohydrate malabsorption and early signs of depression in males. In conclusion, the data confirm that fructose malabsorption may play a role in the development of mental depression in females and additional lactose malabsorption seems to further increase the risk for development of mental depression.     

Development, Validation, and Applicability of a Symptoms Questionnaire for Lactose Malabsorption Screening

Lactase deficiency has a high prevalence worldwide. Thus, a valid symptom scale would be a useful tool for identifying patients with lactose malabsorption. Objective To develop, validate, and apply a symptoms questionnaire on lactose malabsorption to identify lactose malabsorbers diagnosed with the gold-standard hydrogen breath test. Methods In the first part of the study, 292 patients completed a questionnaire at the end of a 50-g lactose breath test. The questionnaire included five items (diarrhea, abdominal cramping, vomiting, audible bowel sounds, and flatulence or gas) scored on a 10-cm visual analogue scale. In the second part of the study, 171 patients completed the questionnaire twice: first, according to their opinion when consuming dairy products at home and second, after a 50-g lactose breath test. Patients were grouped as absorbers or malabsorbers according to the result of the breath test. Results Diarrhea, abdominal cramping, and flatulence were scored significantly higher in malabsorbers than in absorbers. Total score of the symptomatic questionnaire was significantly higher in malabsorbers (17.5 versus 3.0, P < 0.01). According to receiver operator characteristics (ROC) analysis, the most discriminant cut-off of the total score to identify lactose malabsorption was 6.5 (sensitivity 0.75, specificity 0.67). In 58 malabsorbers the effect size of the questionnaire to determine sensitivity to change was 1.32. In the second part of the study, scoring of the home questionnaire was higher than after the lactose-breath test. The lactose malabsorbers rate was higher according to the home questionnaire than after the lactose breath test (72% versus 52%). The home questionnaire had excellent sensitivity (0.82) but low specificity (0.35). Conclusion We developed and validated a five-item symptoms questionnaire for lactose malabsorption. This is a valid test that permits patients with a total score lower than 7 to be excluded from future studies.     

Relationship between methane production and breath hydrogen excretion in lactose-malabsorbing individuals

Recent studies have shown reduced breath hydrogen (H₂) excretion in methane (CH₄)-producing healthy individuals following ingestion of lactulose. This questions the reliability of the breath hydrogen test (BHT) in CH₄ excretors, but the relationship between CH₄ and H₂ excretion in other clinical applications of the BHT is not known. We reviewed BHT results in two groups of subjects: (1) 385 children tested for lactose malabsorption in a hospital setting, and (2) 109 lactose-malabsorbing patients tested with a home kit. The percentage of lactose malabsorbers in group 1 (51%) was the same regardless of CH₄-producing status (P=0.97). The BHT data from group 2 showed a positive correlation (r=0.6, P<0.000001) between the magnitude of the rise in CH₄ and H₂ concentrations, and the H₂ excretion curves were significantly higher in the CH₄-producing individuals. We conclude that attention to CH₄-producing status is not necessary in the interpretation of the lactose BHT.     

Improved Screening for Intestinal Villous Atrophy by d-Xylose Breath Test

The hydrogen breath test (H₂BT) with d-xylose has proven valid in both early recognition and follow-up of intestinal malabsorption. To further evaluate the specificity of the H₂BT with d-xylose in the diagnosis of intestinal malabsorption as compared to the conventional urinary d-xylose test, we analyzed the result in 49 patients referred to our unit with a clinical diagnosis of intestinal malabsorption. These patients had an abnormal 25-g d-xylose H₂BT but a normal conventional urinary d-xylose test. Jejunal biopsy with Watson capsule was performed in all patients. H&E staining was prepared from each biopsy specimen, and histological changes were classified according to the Marsh criteria. Jejunal biopsy showed mucosal atrophy in 5 patients (10%), hyperplastic lesion in 11 (22.5%), infiltrative lesion in 14 (28.5%), and normal appearance in 19 (39%). G. lamblia infection was additionally diagnosed in two patients. Histological changes were independent of the presence of diarrhea, weight loss, abdominal pain, or anemia. H₂ excretion, assessed as increase over baseline and area under the curve, was similarly independent of the histological pattern. In conclusion, performance of a d-xylose H₂BT in patients with a normal urinary test reveals a significant number of patients with intestinal mucosal atrophy who might otherwise remain undiagnosed.     

Comparison of D-Xylose Hydrogen Breath Test With Urinary D-Xylose Test in Indian Children With Celiac Disease

D-xylose hydrogen breath test (H₂BT) may be better parameter in screening for intestinal malabsorption in patients with celiac disease. This study sought to compare D-xylose H₂BT with urinary D-xylose tests in screening for intestinal malabsorption in patients with celiac disease. A total of 68 children with confirmed celiac disease were enrolled for this study. Five-gram urine D-xylose test and D-xylose H₂BT were performed simultaneously according to standard methods. Institute ethical clearance and informed consent was taken before starting this study. Of 68 children, 41 were boys and 27 girls of age range 5–14 years; 5-g urine D-xylose test was abnormal in 50% of cases and 5-g D-xylose H₂BT in 69.9% of cases. D-xylose H₂BT was able to pick up 19.9% more cases of malabsorption in Indian children with celiac disease. This study indicates that performance of 5-g D-xylose H₂BT is a better test than 5-g urinary D-xylose test in screening for intestinal malabsorption in patients with celiac disease.     

Lactase deficiency in Singapore-born and Canadian-born Chinese

Seventy-three of 77 adult Singapore-born Chinese (95%) and 48 of 49 Canadian-born adult Chinese (98%) were demonstrated to be lactase deficient using the lactose breath hydrogen test. The similar prevalence of lactase deficiency in the Singapore- and the Canadian-born Chinese despite a larger estimated amount of daily milk ingestion in the Canadian-born Chinese (430 ml vs 157 ml) supports the concept that lactase deficiency, which is transmitted genetically, does not have an adaptable component related to the quantity of lactose ingested. When the lactose breath hydrogen test performed with a dose of 0.5 g/kg of lactose was compared with the test using a standard dose of 50 g of lactose, there was very little loss of sensitivity. In spite of the presence of lactase deficiency, only 32% of the Singapore subjects and 23% of the Canadian subjects had gastrointestinal symptoms when milk was ingested in the daily diet. Peak breath H₂ was higher in females than males, but the difference was more significant in the Canadian cohort.     

乳糖酶缺乏与乳糖不耐受症状的临床特点分析

目的 探讨乳糖酶缺乏及乳糖不耐受症状的临床特点.方法 回顾性分析了84例于广东省人民医院门诊就诊的以腹痛、腹泻、腹胀、肠鸣为主要症状的患者,并接受胃肠镜、腹部CT、抽血及氢呼气试验等检查评估,根据患者的主要诊断,氢呼气试验结果及乳糖不耐受症状进行分组,比较各组的临床指标,包括年龄、性别、体质量指数、血常规、过敏原检测、...     

Four-sample lactose hydrogen breath test for diagnosis of lactose malabsorption in irritable bowel syndrome patients with diarrhea

AIM: To validate 4-sample lactose hydrogen breath testing (4SLHBT) compared to standard 13-sample LHBT in the clinical setting.METHODS: Irritable bowel syndrome patients with diarrhea (IBS-D) and healthy volunteers (HVs) were enrolled and received a 10 g, 20 g, or 40 g dose lactose hydrogen breath test (LHBT) in a randomized, double-blinded, controlled trial. The lactase gene promoter region was sequenced. Breath samples and symptoms were acquired at baseline and every 15 min for 3 h (13 measurements). The detection rates of lactose malabsorption (LM) and lactose intolerance (LI) for a 4SLHBT that acquired four measurements at 0, 90, 120, and 180 min from the same data set were compared with the results of standard LHBT.RESULTS: Sixty IBS-D patients and 60 HVs were studied. The genotype in all participants was C/C-13910. LM and LI detection rates increased with lactose dose from 10 g, 20 g to 40 g in both groups (P < 0.001). 4SLHBT showed excellent diagnostic concordance with standard LHBT (97%-100%, Kappa​​ 0.815-0.942) with high sensitivity (90%-100%) and specificity (100%) at all three lactose doses in both groups.CONCLUSION: Reducing the number of measurements from 13 to 4 samples did not significantly impact on the accuracy of LHBT in health and IBS-D. 4SLHBT is a valid test for assessment of LM and LI in clinical practice.     

A Diagnostic Approach to Patients with Suspected Lactose Malabsorption

Background

The lactose breath test (LBT) is the standard technique for diagnosis of lactose malabsorption. However, it is time-consuming, strenuous for the patient and has been reported to have low sensitivity. The lactose intolerance quick test (LIQT) measures lactase activity in duodenal biopsies and may be performed as part of upper gastrointestinal endoscopy.

Aim

The purpose of this study was to assess the role of the LBT and LIQT in the case management of suspected lactose malabsorption.

Methods

The study group included 69 consecutive patients evaluated by the LBT followed by the LIQT. The test results were compared, and the sensitivity, specificity, and predictive values of the LBT were calculated.

Results

Mean age of the patients was 54.4 years, male/female ratio was 1:3, and mean body mass index was 25.2. None had celiac disease on duodenal biopsy. The LIQT was positive for hypolactasia in 55 patients (80 %): mild in 14 (25 %) and severe in 41 (75 %); 10 (18 %) were symptomatic during the LBT. The LBT was positive for lactose malabsorption in 32 patients (46 %). Of the 37 patients with normal findings on the LBT, 24 (65 %) had positive findings on the LIQT: 11 (30 %) mild hypolactasia, 13 (35 %) severe hypolactasia. In one case, the LBT was positive and the LIQT was negative. The LBT had a sensitivity of 56 %, specificity 93 %, positive predictive value 97 %, and negative predictive value 35 %.

Conclusions

The LBT may serve as a diagnostic screening tool for lactose malabsorption. Symptomatic patients with negative LBT results should be referred for second-line testing with the LIQT.     

Lactose Malabsorption in Patients Operated Upon for Peptic Ulcer

A lactose tolerance test was performed and small intestinal mucosal disaccharidase activity was determined in 12 patients operated upon for peptic ulcer who had lactose malabsorption. Most patients were misjudged, since they were considered to suffer from post-operative complaints (vagotomy diarrhoea, afferent loop syndrome, recurrent ulcer and dumping). Three patients did not develop symptoms of milk intolerance until immediately after an operation for peptic ulcer; in 3 other patients this operation exacerbated the existing symptoms after consumption of milk. Two patients had steatorrhoea, which disappeared or diminished when lactose excluded from the diet.     

Prediction of lactose malabsorption in referral patients

Two hundred forty-two patients referred for various gastrointestinal complaints were evaluated for clinical parameters that would predict findings of lactose malabsorption. Breath hydrogen and blood glucose lactose tests were performed after ingestion of 50 g lactose. Presenting complaints, duration of symptoms, and patient demographics such as age, sex, and ethnic heritage were not different between lactose malabsorbers and absorbers as defined by the breath hydrogen lactose test. Foodrelated symptoms in general and after specific foods such as milk, ice cream, cheese, and yogurt were also similar between groups. Prior to testing, 30% of malabsorbers (N=161) and 36% of absorbers (N=81) reported lactoserelated symptoms (P=NS). The blood glucose response to lactose was abnormal in 60% of malabsorbers and 15% of absorbers. This study confirmed our impression that it is difficult to predict lactose absorption status by clinical parameters. The majority of our lactose malabsorber patients were unaware of lactose-associated symptoms. Furthermore, symptom assessment, demographics, food history, and blood glucose testing did not predict abnormal hydrogen responses to lactose.The opinions and assertations expressed herein are those of the authors and are not to be construed as reflecting opinions of the United States Air Force or the Department of Defense.This work has been presented in part at the Annual Scientific Session of the American Gastroenterological Association, San Francisco, California, May 19, 1986, and published as an abstract (Gastroenterology 90:1562, 1986).     

Small Intestinal Bacterial Overgrowth and Lactose Intolerance Contribute to Irritable Bowel Syndrome Symptomatology in Pakistan

Background /Aim:

The symptoms of irritable bowel syndrome resemble those of small intestinal bacterial overgrowth (SIBO). The aim of this study was to determine the frequency of SIBO and lactose intolerance (LI) occurrence in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) according to Rome III criteria.

Patients and Methods:

In this retrospective case-control study, patients over 18 years of age with altered bowel habit, bloating, and patients who had lactose Hydrogen breath test (H₂BT) done were included. The “cases” were defined as patients who fulfill Rome III criteria for IBS-D, while “controls” were those having chronic nonspecific diarrhea (CNSD) who did not fulfill Rome III criteria for IBS-D. Demographic data, predominant bowel habit pattern, concurrent use of medications, etc., were noted.

Results:

Patients with IBS-D were 119 (51%) with a mean age of 35 ± 13 years, while those with CNSD were 115 (49%) with mean age 36 ± 15 years. Patients in both IBS-D and CNSD were comparable in gender, with male 87 (74%) and female 77 (64%). SIBO was documented by lactose H₂BT in 32/234 (14%) cases. It was positive in 22/119 (19%) cases with IBS-D, while 10/115 (9%) cases had CNSD (P = 0.03). LI was positive in 43/234 (18%) cases. Of these, 25/119 (21%) cases had IBS-D and 18/115 (16%) cases had CNSD (P = 0.29).

Conclusion:

SIBO was seen in a significant number of our patients with IBS-D. There was no significant age or gender difference in patients with or without SIBO.     

Inverse Dose Effect of Pretest Dietary Lactose Intake on Breath Hydrogen Results and Symptoms in Lactase Nonpersistent Subjects

The aim of this study was to determine a relationship between pretest intake of lactose and outcome of lactose breath hydrogen test. Patients presented at a testing laboratory participated in the study. A 3-hour breath hydrogen, 50-g lactose challenge was carried out. Results were tabulated and patients completed a 3-day recall diet questionnaire. Daily lactose intake was independently calculated and was associated with breath hydrogen and total symptom score. Statistical analysis used Spearman's correlation, Mann-Whitney U-test and χ² or Fisher exact test. Of 118 patients, 50% were lactose maldigesters. In these patients, measured breath hydrogen and symptom scores were significantly higher in the lowest intake group (< 5 g/d) than in the highest intake group (> 20 g/d) (P < .05). In the presumed lactose digesters, 59% experienced some symptoms during testing for unclear reasons. Pretest dietary intake of lactose inversely affects results of breath hydrogen.     

Rifaximin in patients with lactose intolerance

BACKGROUND: Abdominal symptoms linked to lactose malabsorption may be caused by metabolic activity of colonic bacteria. Rifaximin, a non-absorbable rifampycin derivative, is active against colonic bacteria, it may be useful in the treatment of lactose intolerance. AIM: The aim of this study has been to evaluate short-term rifaximin therapy in patients with lactose intolerance. METHODS: Thirty-two patients with lactose intolerance diagnosed using the hydrogen lactose breath test were studied. Fourteen patients received rifaximin 800 mg/day for 10 days, 13 patients followed a diet without milk for 40 days and 5 patients received a placebo for 10 days. Total breath H(2) excretion expressed as area under the curve, and the symptom score were evaluated in all patients at the start, and subsequently after 10 and 40 days. RESULTS: In the 14 patients who received rifaximin for 10 days, area under the curve at day 10 and day 40 was statistically significantly lower than the one computed at basal (P<0.01). Diet reduced area under the curve progressively reaching statistical significance at day 40, while the placebo did not change area under the curve throughout the study. The total symptom score significantly improved after rifaximin and diet. CONCLUSION: In patients with lactose intolerance, a 10-day therapy with rifaximin as well as 40-day diet without lactose reduces the area under the curve and the symptom score.     

Lactose intolerance: Lactose tolerance test versus genotyping

Objective

Adult lactose intolerance, which affects the majority of the population in the world, has been associated with a single nucleotide polymorphism, C-13910T, located upstream of the lactase gene.

Material and methods

Adult patients undergoing lactose tolerance tests with lactose challenge and plasma glucose measurements were included in the study comprising 44 Swedes and 7 non-Swedish individuals. A real-time PCR method was established for the genotyping.

Results

Out of 51 patients 48 had concordant results on genotyping and lactose tolerance tests, e.g. ?13910T/T and ?13910C/T genotypes had high glucose elevations. All patients with the heterozygous genotype, ?13910C/T, had high glucose elevations, and no gene–dose relationship was observed when comparing maximal glucose increases for cases with ?13910C/T and ?13910T/T genotypes.

Conclusions

Genotyping could replace lactose challenge as a first-stage screening test in adults of European descent, but should be used together with tolerance tests in children and patients where secondary lactose intolerance is suspected.     

Effects of age on lactose malabsorption in Oklahoma Native Americans as determined by breath H2 analysis

Breath H₂ excretion was used to determine lactose malabsorption in 30 healthy females and 30 healthy males between the ages of 3 and 64 yr who were at least 7/8 Native American. The test meal consisted of 5 ml reconstituted nonfat dry milk (0.25 g lactose) per kg of body weight. On the basis of breath H₂ tests in 15 control subjects with normal oral lactose tolerance tests, a response factor of 20 ppm was selected as the upper limit for lactose absorbers. Of the 60 subjects in the study group, 36 (60%) were classified as lactose malabsorbers since they had a response factor of 20 ppm or greater of breath H₂. Only 3 of 20 children (15%) who were under the age of 12 yr were nondigesters of the small lactose dose used in this study. Approximately 82 percent (82.5%) of subjects who were 13 yr and older were lactose malabsorbers. Adolescence appears to be the period in which malabsorption of lactose becomes evident in Native North Americans.Supported by the Nutrition Foundation, Inc., New York, New York; Biomedical Sciences Support Grant (USPH) 5-S05-RR7077 to The Research Foundation, Oklahoma State University.     

Breath tests and irritable bowel syndrome

Breath tests are non-invasive tests and can detect H2and CH4 gases which are produced by bacterial fermentation of unabsorbed intestinal carbohydrate and are excreted in the breath.These tests are used in the diagnosis of carbohydrate malabsorption,small intestinal bacterial overgrowth,and for measuring the orocecal transit time.Malabsorption of carbohydrates is a key trigger of irritable bowel syndrome(IBS)-type symptoms such as diarrhea and/or constipation,bloating,excess flatulence,headaches and lack of energy.Abdominal bloating is a common nonspecific symptom which can negatively impact quality of life.It may reflect dietary imbalance,such as excess fiber intake,or may be a manifestation of IBS.However,bloating may also represent small intestinal bacterial overgrowth.Patients with persistent symptoms of abdominal bloating and distension despite dietary interventions should be referred for H2 breath testing to determine the presence or absence of bacterial overgrowth.If bacterial overgrowth is identified,patients are typically treated with antibiotics.Evaluation of IBS generally includes testing of other disorders that cause similar symptoms.Carbohydrate malabsorption(lactose,fructose,sorbitol)can cause abdominal fullness,bloating,nausea,abdominal pain,flatulence,and diarrhea,which are similar to the symptoms of IBS.However,it is unclear if these digestive disorders contribute to or cause the symptoms of IBS.Research studies show that a proper diagnosis and effective dietary intervention significantly reduces the severity and frequency of gastrointestinal symptoms in IBS.Thus,diagnosis of malabsorption of these carbohydrates in IBS using a breath test is very important to guide the clinician in the proper treatment of IBS patients.