Prevalence of liver injury and correlation with clinical outcomes in patients with COVID-19: systematic review with meta-analysis.

OBJECTIVE: Liver involvement of SARS-CoV-2 infection has been reported in several papers, but without homogeneous findings. We aimed to systematically review the prevalence of liver involvement in patients with SARS-CoV-2 infection at their hospital admission, and its correlation with disease severity and clinical outcomes in patients with or without pre-existing chronic liver disease. MATERIALS AND METHODS: We systematically searched PubMed, Embase, Web of Science, Medline, PMC, clinical trial registries, and other Coronavirus family publications for studies reporting data on SARS-CoV-2 infection or COVID-19 and liver function tests (LFTs) alterations, as well as clinical course of patients with chronic liver disease or cirrhosis. Case reports, preprints, editorials, reviews were excluded. We also revised literature to describe the background of liver involvement during SARS-CoV-2 infection. RESULTS: 36 studies, including 20724 patients with SARS-CoV-2 infection, were included. The pooled prevalence of LFTs abnormalities at admission was 46.9% (AST 26.5%, ALT 22.8%, GGT 22.5%, ALP 5.7%, tBIL 8.0%). ALT, AST, tBIL were independent predictors of disease severity (ALT OR 1.54, 95% CI 1.17-2.03; AST OR 3.17, 95% CI 2.10-4.77; tBIL OR 2.32, 95% CI 1.18-4.58) and in-hospital mortality (ALT OR 1.48, 95% CI 1.12-1.96; AST OR 4.39, 95% CI 2.68-7.18; tBIL OR 7.75, 95% CI 2.28-26.40). Heterogeneity among studies was high. The few available data also reported that COVID-19 was associated with increased risk of liver decompensation and mortality in patients with liver cirrhosis. CONCLUSIONS: LFTs alterations were reported in up to 47% of unselected patients with COVID-19 and were associated with severe disease or in-hospital mortality. In cirrhotic patients, COVID-19 was associated with high risk of liver decompensation or mortality.

Helicobacter pylori infection is associated with high methane production during lactulose breath test.

OBJECTIVE: Despite a growing interest toward the interplay between H. pylori and gastric microbiota, few data are available about this correlation. The aim of this study was to explore the relationship between H. pylori infection and gas production during lactulose breath test. MATERIALS AND METHODS: Data of patients undergoing both 13C-urea breath test (UBT) and lactulose breath test (LBT) under standard conditions in our GI unit were retrospectively analyzed. GI symptoms, such as dyspepsia, bloating, abdominal pain/discomfort, and epigastric pain on an eleven-point scale were also analyzed and correlate with the results of those tests. H2 and CH4 were calculated using the trapezoidal rule; a considerable CH4 production was defined by AUCCH4 ≥1200 ppm*4h. Statistical analyses were performed with Fisher's exact test and independent samples Mann-Whitney test. RESULTS: Data of 136 patients during a period of time of 3 months were analyzed. 36 patients (26.5%) showed a positive UBT. We do not find any difference as regards age, sex, symptom complaints, and small intestinal bacterial overgrowth between HP negative and positive patients. A greater methane production was observed in infected rather than non-infected patients (47.2% vs. 26% respectively, p=0.02). Furthermore, 25% infected and 10% non-infected produced greater amounts of CH4 compared to H2, resulting in a AUCCH4/AUCH2 ratio >1 (p=0.046). CONCLUSIONS: This study shows for the first time, a significant association between H. pylori infection and methane production, suggesting that H. pylori might influence gut microbiota composition. Further studies are needed to clarify mechanisms underlying this phenomenon.

Specific 13C functional pathways as diagnostic targets in gastroenterology breath-tests: tricks for a correct interpretation.

Breath tests are non-invasive, non-radioactive, safe, simple and effective tests able to determine significant metabolic alterations due to specific diseases or lack of specific enzymes. Carbon isotope (13)C, the stable-non radioactive isotope of carbon, is the most used substrate in breath testing, in which (13)C/(12)C ratio is measured and expressed as a delta value, a differences between readings and a fixed standard. (13)C/(12)C ratio is measured with isotope ratio mass spectrometry or non-dispersive isotope-selective infrared spectrometer and generally there is a good agreement between these techniques in the isotope ratio estimation. (13)C/(12)C ratio can be expressed as static measurement (like delta over baseline in urea breath test) or as dynamic measurement as percent dose recovery, but more dosages are necessary. (13)C Breath-tests are involved in many fields of interest within gastroenterology, such as detection of Helicobacter pylori infection, study of gastric emptying, assessment of liver and exocrine pancreatic functions, determination of oro-caecal transit time, evaluation of absorption and to a lesser extend detection of bacterial overgrowth. The use of every single test in a clinical setting is vary depending on accuracy and substrate costs. This review is meant to present (13)C the meaning of (13)C/(12)C ratio and static and dynamic measure and, finally, the instruments dedicated to its use in gastroenterology. A brief presentation of (13)C breath tests in gastroenterology is also provided.

Tricks for interpreting and making a good report on hydrogen and 13C breath tests.

Breath tests (BT) represent a valid and non-invasive diagnostic tool in many gastroenterological disorders. Their wide diffusion is due to the low cost, simplicity and reproducibility and their common indications include diagnosis of carbohydrate malabsorption, Helicobacter pylori infection, small bowel bacterial overgrowth, gastric emptying time and orocaecal transit time. The review deals with key points on methodology, which would influence the correct interpretation of the test and on a correct report. While a clear guideline is available for lactose and glucose breath tests, no gold standard is available for Sorbitol, Fructose or other H2 BTs. Orocaecal transit time (OCTT) defined as time between assumption of 10 g lactulose and a peak > 10 ppm over the baseline value, is a well-defined breath test. The possible value of lactulose as a diagnostic test for the diagnosis of small bowel bacterial overgrowth is still under debate. Among (13)C breath test, the best and well characterized is represented by the urea breath test. Well-defined protocols are available also for other (13)C tests, although a reimbursement for these tests is still not available. Critical points in breath testing include the patient preparation for test, type of substrate utilized, reading machines, time between when the test is performed and when the test is processed. Another crucial point involves clinical conclusions coming from each test. For example, even if lactulose could be utilized for diagnosing small bowel bacterial overgrowth, this indication should be only secondary to orocaecal transit time, and added into notes, as clinical guidelines are still uncertain.