Aigars Vanags

Breath testing as potential colorectal cancer screening tool

Although colorectal cancer (CRC) screening is included in organized programs of many countries worldwide, there is still a place for better screening tools. In this study, 418 breath samples were collected from 65 patients with CRC, 22 with advanced or nonadvanced adenomas, and 122 control cases. All patients, including the controls, had undergone colonoscopy. The samples were analysed with two different techniques. The first technique relied on gas chromatography coupled with mass spectrometry (GC‐MS) for identification and quantification of volatile organic compounds (VOCs). The T‐test was used to identify significant VOCs (p values < 0.017). The second technique relied on sensor analysis with a pattern recognition method for building a breath pattern to identify different groups. Blind analysis or leave‐one‐out cross validation was conducted for validation. The GC‐MS analysis revealed four significant VOCs that identified the tested groups; these were acetone and ethyl acetate (higher in CRC), ethanol and 4‐methyl octane (lower in CRC). The sensor‐analysis distinguished CRC from the control group with 85% sensitivity, 94% specificity and 91% accuracy. The performance of the sensors in identifying the advanced adenoma group from the non‐advanced adenomas was 88% sensitivity, 100% specificity, and 94% accuracy. The performance of the sensors in identifying the advanced adenoma group was distinguished from the control group was 100% sensitivity, 88% specificity, and 94% accuracy. For summary, volatile marker testing by using sensor analysis is a promising noninvasive approach for CRC screening.

Breath Testing as Potential Colorectal Cancer Screening Tool

Although colorectal cancer (CRC) screening is included in organized programs of many countries worldwide, there is still a place for better screening tools. In this study, 418 breath samples were collected from 65 patients with CRC, 22 with advanced or nonadvanced adenomas, and 122 control cases. All patients, including the controls, had undergone colonoscopy. The samples were analysed with two different techniques. The first technique relied on gas chromatography coupled with mass spectrometry (GC‐MS) for identification and quantification of volatile organic compounds (VOCs). The T‐test was used to identify significant VOCs (p values < 0.017). The second technique relied on sensor analysis with a pattern recognition method for building a breath pattern to identify different groups. Blind analysis or leave‐one‐out cross validation was conducted for validation. The GC‐MS analysis revealed four significant VOCs that identified the tested groups; these were acetone and ethyl acetate (higher in CRC), ethanol and 4‐methyl octane (lower in CRC). The sensor‐analysis distinguished CRC from the control group with 85% sensitivity, 94% specificity and 91% accuracy. The performance of the sensors in identifying the advanced adenoma group from the non‐advanced adenomas was 88% sensitivity, 100% specificity, and 94% accuracy. The performance of the sensors in identifying the advanced adenoma group was distinguished from the control group was 100% sensitivity, 88% specificity, and 94% accuracy. For summary, volatile marker testing by using sensor analysis is a promising noninvasive approach for CRC screening.

Gastric plasma biomarkers and Operative Link for Gastritis Assessment gastritis stage.

Introduction The Operative Link for Gastritis Assessment (OLGA) staging system has been proposed as a histopathological reporting system of gastric atrophy. Noninvasive methods for indirect evaluation of gastric mucosal atrophy by biomarkers are also being introduced. Objectives To analyze gastric mucosal atrophy by biomarkers, pepsinogen I (PgI), pepsinogen II (PgII), PgI/PgII ratio, fasting gastrin-17 (G-17), stimulated gastrin-17 (sG-17), in relation to OLGA gastritis stage. Patients and methods Gastric biopsies were taken from 269 prospective patients referred for upper endoscopy because of dyspeptic problems and evaluated by two expert pathologists (D.J. and P.S.). Atrophy was assessed according to the OLGA staging system. Pg I, PgII, Pg I/II, G-17, sG-17 were determined in a plasma sample. Results The mean levels of PgI and PgI/PgII decreased significantly from 90.8 &mgr;g/l and 7.6 in stage 0 gastritis to 64.3 &mgr;g/l and 4.3 in high-stage gastritis. The mean values of G-17 and sG-17 were significantly higher among patients with stage II gastritis compared with stage 0 and high-stage gastritis. The proportion of patients with normal mucosa and nonatrophic gastritis according to biomarkers decreased from 78% in stage 0 to 22% in high-stage (III–IV) gastritis. Among the latter no case with normal mucosa, according to biomarkers, was observed. Conclusions A significant inverse correlation between the mean levels of PgI, PgI/II ratio and the OLGA stage was observed. Percentage of dyspeptic patients with normal mucosa, by blood biomarkers, decreased with increasing OLGA gastritis stages. OLGA staging system provides a good frame for scientific analysis of gastric mucosal atrophy.

The effect of incisura angularis biopsy sampling on the assessment of gastritis stage.

Objectives It is important to stratify patients according to the magnitude of risk for gastric cancer development; the OLGA (Operative Link for Gastritis Assessment) and OLGIM (Operative Link on Gastric Intestinal Metaplasia) staging systems of lesions in the stomach mucosa have been proposed for this purpose. There are some discrepancies in the current guidelines regarding the value of incisura angularis biopsies. The aim of our study was to assess the value of incisura angularis biopsy in staging gastritis according to the OLGA and OLGIM systems by examining the atrophic, metaplastic and inflammatory changes in the antrum, incisura angularis and corpus. Patients and methods We enrolled 835 patients undergoing upper endoscopy. Three expert gastrointestinal pathologists graded biopsy specimens according to the Sydney classification and the stage of gastritis was assessed by the OLGA and OLGIM systems. Results The results demonstrated that severe atrophic, metaplastic and chronic inflammatory changes were more frequently observed in the incisura angularis mucosa than in the antrum or corpus mucosae (P<0.05). There was a general downgrading of stage by 18.0% for OLGA and by 4.0% for OLGIM when the incisura angularis was excluded from the staging. Furthermore, there was a 30–35% downgrading for high-risk OLGA/OLGIM stages. Conclusion The incisura angularis undergoes more severe atrophic, metaplastic and chronic inflammatory changes than the antrum and corpus. Incisura angularis biopsies should be routinely included in the biopsy sampling protocol.

Analysis of the effects of microbiome-related confounding factors on the reproducibility of the volatolomic test.

Volatile organic compound (VOC) testing in breath has potential in gastric cancer (GC) detection. Our objective was to assess the reproducibility of VOCs in GC, and the effects of conditions modifying gut microbiome on the test results. Ten patients with GC were sampled for VOC over three consecutive days; 17 patients were sampled before and after H. pylori eradication therapy combined with a yeast probiotic; 61 patients were sampled before and after bowel cleansing (interventions affecting the microbiome). The samples were analyzed by: (1) gas chromatography linked to mass spectrometry (GC-MS), applying the non-parametric Wilcoxon test (level of significance p  <  0.05); (2) by cross-reactive nanoarrays combined with pattern recognition. Discriminant function analysis (DFA) was used to build the classification models; and leave-one-out cross-validation analysis was used to classify the findings. Exhaled VOCs profiles were stable for GC patients over a three day period. Alpha pinene (p  =  0.028) and ethyl acetate (p  =  0.030) increased after the antibiotic containing eradication regimen; acetone (p  =  0.0001) increased following bowel cleansing prior to colonoscopy. We further hypothesize that S. boulardii given with the standard eradication regimen to re-establish the gut microbiome was the source for long-term ethyl acetate production. Differences between the initial and the follow-up sample were also revealed in the DFA analysis of the sensor data. VOC measurement results are well-reproducible in GC patients indicating a useful basis for potential disease diagnostics. However, interventions with a potential effect on the gut microbiome may have an effect upon the VOC results, and therefore should be considered for diagnostic accuracy.

Detection of gastric atrophy by circulating pepsinogens: A comparison of three assays

Circulating levels of pepsinogens have been used in high gastric cancer‐risk Asian and European populations to triage endoscopic evaluation for more severe pathology. There are different analytic methods with uncertain correlations. We therefore compared diagnostic performance of three commonly used pepsinogen assays to detect histologically confirmed gastric atrophy.

Accuracy of two plasma antibody tests and faecal antigen test for non-invasive detection of H. pylori in middle-aged Caucasian general population sample

Abstract Objective: The aim of the study was to assess the accuracy of two plasma Helicobacter pylori (H. pylori) antibody test-systems and a stool antigen test (SAT) system in a general population sample in Latvia. Materials and methods: Blood and faecal samples were analysed in healthy individuals (40–64 years), referred for upper gastrointestinal endoscopy according to pilot study protocol within a population-based study investigating gastric cancer prevention strategies (GISTAR pilot study). Antibodies to H. pylori were assessed in plasma by latex-agglutination test and enzyme-linked immunosorbent assay (ELISA). H. pylori antigen in faecal samples was detected by a monoclonal enzyme immunoassay-based SAT. Histological assessment of H. pylori based on a modified Giemsa staining method was used as the gold standard. Individuals having received H. pylori eradication within one year prior to enrolment were excluded. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy were calculated. Receiver-operating characteristic curves were designed to estimate the optimal diagnostic cut-off value of tests. Results: The analysis included 779 participants for latex-agglutination test, 1002 for ELISA and 672 individual samples for SAT. The sensitivity, specificity, PPV, NPV and overall accuracy were as follows: latex-agglutination test (86;81;87;80;84%), ELISA (97;72;83;94;86%) and SAT (87;81;87;81;85%), respectively. The optimal diagnostic cut-off value for ELISA test was ≥50.26 g/L. Conclusions: Although the performance of the three tests was comparable to each other, the three test systems showed suboptimal accuracy, with important implications for public health programs based on ‘test-and-treat’ strategy.

Sa1896 Nanomaterial-Based Sensor Technology Can Detect Gastric Cancer and Peptic Ulcer Disease With a High Accuracy From an Exhaled Air Sample

BACKGROUND. Early and non-invasive detection of gastric cancer (GC) is remaining a challenge in many high-risk areas. OBJECTIVES. To investigate the feasibility of gastric cancer and peptic ulcer disease detection by measuring volatile organic compounds (VOCs) in the exhaled breath by a nanomaterial-based sensor technology. METHODS. Alveolar exhaled breath samples were collected from 99 GC patients, 53 peptic ulcer disease (PUD) patients and 342 controls in Latvia (Caucasian population) having been investigated by upper endoscopy. Nanomaterial-based sensors Gold nano particles (GNP) and single-wall carbon nanotube (SWCNT) were used to discriminate the GC and the PUD groups from the healthy controls by loading discriminant factor analysis (DFA) pattern recognition. Classification success was calculated by (i) building an algorithm for 70% of the samples as a training set and (ii) randomly blinding 30% of the samples as a validation set. RESULTS. The blind DFA models showed: (i) An excellent discrimination between the GC patients and controls (91% accuracy); (ii) An excellent discrimination between the GC patients and PUD patients (86% accuracy); (iii) Good discrimination between the PUD patients and controls (80% accuracy). CONCLUSIONS: The obtained results are demonstrating the good potential of VOC detection in exhaled breath by nanomaterial-based sensor technology in diagnosing GC and PUD. Performance characteristics of nanomaterial-based sensor technology to detect gastric cancer and peptic ulcer disease