Introduction
Lactose malabsorption (LM) is a common digestive disorder. The hydrogen breath test (HBT) is currently the non-invasive gold standard in diagnosing LM and lactose intolerance (LI), which is defined only in case of developing symptoms directly related to lactose ingestion in subjects with LM. (Misselwitz et al. 2019) The analysis of methane values in air samples may increase the accuracy of the test by including subjects “non hydrogen producers”. (De Geyter et al. 2021)
Aims & Methods
The aim of this study is to describe the relationship between pre-test clinical features, symptoms reported during lactose challenge and the result of the HBT in adults. In this prospective study we included a consecutive series of adult patients who underwent a HBT during a 5-month period. Air samples were taken every 30 minutes for 4 hours after the ingestion of a charge of 25 g of lactose. Symptoms reported in the previous 15 days (abdominal pain, bloating, diarrhoea, flatulence) and those experienced after lactose ingestion were assessed using a standard questionnaire establishing their presence or absence, and relative severity using 0-10 scale. The results were considered positive when a H2 peak exceeded 20 parts per million (ppm) above the baseline or in case CH4 excretion reached 10 ppm above the baseline, for experimental purpose. LI was defined by at least one symptom experienced during the test in subjects with LM.
Results
68 patients were included in the study and 40 of them (59%) were positive at the HBT. 52 (76%) developed at least one symptom while LI was diagnosed in 34 patients of them (65%). Only 40% of patients who referred pre-test symptoms had LM and none of the four symptoms was associated with LM or LI. A positive trend was found between abdominal bloating after lactose ingestion and a positive HBT (p 0.08). This association was statistically significant (73% vs 43%, p 0.02), with a positive trend also for flatulence (p 0.08) (Table), implementing diagnostic test with values of exhaled methane, finding 10 more intolerant patients. Considering the variation of symptoms (new or worsening of symptoms after lactose ingestion), the worsening of bloating was significantly more frequent in subjects with positive HBT compared to those with a negative test (40% vs 14%, p 0.03) and predictive of LI (PPV= 80%). Diarrhoea was the most predictive symptom of LI (PPV up to 88%). An association between the number of symptoms experienced during the test and LM was confirmed, while we didn’t find the same relationship with pre-test symptoms. (Beyerlein et al. 2008)
| Symptoms during the test | Total number of patients. N=68 | positive H2 /CH4 BT , N=45
| negative H2 /CH4 BT-, N=23
| p value |
| Abdominal pain | 38 (56%) | 28 (62%) | 10 (43%) | non statistically significant |
| Abdominal bloating | 43 (63%) | 33 (73%) | 10 (43%) | 0,02 |
| Flatulence | 40 (59%) | 30 (67%) | 10 (43%) | 0,08 |
| Diarrhoea | 12 (18%) | 10 (22%) | 2 (9%) | non statistically significant
|
Conclusion
Symptoms reported before HBT seems to be non-related to LI. This may lead to arbitrary dietary exclusion of dairy products with consequences on bone health (Infante and Tormo 2000) and suggest that the causal role of lactose should be confirmed by HBT. In adult, the development ex-novo or the exacerbation of abdominal bloating and diarrhoea during the test, in subjects with LM, seems to be the most predictive of LI. Furthermore, the increase of the number of symptoms complained makes the diagnosis of LI more likely. On these basis, a domestic screening with 25 g of lactose (500 ml of milk) to establish whether the patient really needs the execution of breath test should be explored.
References
Beyerlein et al. 2008
De Geyter et al. 2021
Infante and Tormo 2000
Misselwitz et al. 2019