Early detection and follow-up of colorectal neoplasia based on faecal volatile organic compounds.

AIM: Early detection and removal of colorectal cancer (CRC) and advanced adenomas (AAs) decreases the incidence of and mortality from the disease. We aimed to evaluate the potential of faecal volatile organic compounds (VOCs) for detection and follow-up of colorectal adenoma using advanced electronic nose technology. METHOD: This was a prospective multi-centre case-control cohort including two district hospitals and one tertiary referral hospital. Patients undergoing colonoscopy were instructed to collect a faecal sample prior to bowel cleansing and were included in the study when CRC, AAs, large adenomas (LAs; 0.5-1.0 cm), small adenomas (SAs; 0.1-0.5 cm) or no endoscopic abnormalities (controls) were observed. Patients undergoing polypectomy and controls were asked for a second sample after 3 months. Faecal VOCs were measured with gas chromatography-ion mobility spectrometry. Random forest, support vector machine, Gaussian process and neural net classification were used to evaluate accuracy. RESULTS: In total, 14 patients with CRC, 64 with AAs, 69 with LAs, 127 with SAs and 227 controls were included. A second sample was collected from 32 polypectomy patients and 32 controls. Faecal VOCs discriminated CRC and adenomas from control [AUC (95% CI): CRC vs control 0.96 (0.89-1); AA vs control 0.96 (0.93-1); LA vs control 0.96 (0.92-0.99); SA vs control 0.96 (0.94-0.99)]. There were no significant differences between CRC and adenoma groups. Patients with adenomas and controls were discriminated prior to polypectomy, whereas 3 months after polypectomy VOC profiles were similar [T0 adenoma vs control 0.98 (0.95-1); T1 adenoma vs control 0.55 (0.40-0.69)]. CONCLUSIONS: Faecal VOC profiles may be useful for early detection of CRC and adenomas and the timing of polyp surveillance as polypectomy led to a normalization of the VOC profile.

Urinary volatile organic compound markers and colorectal anastomotic leakage.

AIM: Inflammatory markers such as serum C-reactive protein (CRP) are used as routine markers to detect anastomotic leakage following colorectal surgery. However, CRP is characterized by a relatively low predictive value, emphasizing the need for the development of novel diagnostic approaches. Volatile organic compounds (VOCs) are gaseous metabolic products deriving from all conceivable bodily excrements and reflect (alterations in) the patient's physical status. Therefore, VOCs are increasingly considered as potential non-invasive diagnostic biomarkers. The aim of this study was to assess the diagnostic accuracy of urinary VOCs for colorectal anastomotic leakage. METHODS: In this explorative multicentre study, urinary VOC profiles of 22 patients with confirmed anastomotic leakage and 27 uneventful control patients following colorectal surgery were analysed by field asymmetric ion mobility spectrometry (FAIMS). RESULTS: Urinary VOCs of patients with anastomotic leakage could be distinguished from those of control patients with high accuracy: area under the receiver operating characteristics curve 0.91 (95% CI 0.81-1.00, P < 0.001), sensitivity 86% and specificity 93%. Serum CRP was significantly increased in patients with a confirmed anastomotic leak but with lower diagnostic accuracy compared to VOC analysis (area under the receiver operating characteristics curve 0.82, 95% CI 0.68-0.95, P < 0.001). Combining VOCs and CRP did not result in a significant improvement of the diagnostic performance compared to VOCs alone. CONCLUSION: Analysis by FAIMS allowed for discrimination between urinary VOC profiles of patients with a confirmed anastomotic leak and control patients following colorectal surgery. A superior accuracy compared to CRP and apparently high specificity was observed, underlining the potential as a non-invasive biomarker for the detection of colorectal anastomotic leakage.

Colorectal cancer and adenoma screening using urinary volatile organic compound (VOC) detection: early results from a single-centre bowel screening population (UK BCSP).

BACKGROUND: The United Kingdom (UK) bowel cancer screening programme has reduced mortality from colorectal cancer (CRC), but poor uptake with stool-based tests and lack of specificity of faecal occult blood testing (FOBT), has prompted investigation for a more suitable screening test. The aim of this study was to investigate the feasibility of a urinary volatile organic compounds (VOC)-based screening tool for CRC. METHODS: The urine from FOBT-positive patients was analysed using field asymmetric ion mobility spectrometry (FAIMS) and gas chromatography coupled with ion mobility spectrometry (GC-IMS). Data were analysed using a machine learning algorithm to calculate the test accuracy for correct classification of CRC against adenomas and other gastrointestinal pathology. RESULTS: One hundred and sixty-three patients were enrolled in the study. Test accuracy was high for differentiating CRC from control: area under the curve (AUC) 0.98 (95% CI 0.93-1) and 0.82 (95% CI 0.67-0.97) using FAIMS and GC-IMS respectively. Correct classification of CRC from adenoma was high with AUC range 0.83-0.92 (95% CI 0.43-1.0). Classification of adenoma from control was poor with AUC range 0.54-0.61 (95% CI 0.47-0.75) using both analytical modalities. CONCLUSIONS: CRC was correctly distinguished from adenomas or no bowel pathology using urinary VOC markers, within the bowel screening population. This pilot study demonstrates the potential of this method for CRC detection, with higher test uptake and superior sensitivity than FOBT. In addition, this is the first application of GC-IMS in CRC detection which has shown high test accuracy and usability.

Risk stratification of symptomatic patients suspected of colorectal cancer using faecal and urinary markers.

AIM: Faecal markers, such as the faecal immunochemical test for haemoglobin (FIT) and faecal calprotectin (FCP), have been increasingly used to exclude colorectal cancer (CRC) and colonic inflammation. However, in those with lower gastrointestinal symptoms there are considerable numbers who have cancer but have a negative FIT test (i.e. false negative), which has impeded its use in clinical practice. We undertook a study of diagnostic accuracy CRC using FIT, FCP and urinary volatile organic compounds (VOCs) in patients with lower gastrointestinal symptoms. METHOD: One thousand and sixteen symptomatic patients with suspected CRC referred by family physicians were recruited prospectively in accordance with national referring protocol. A total of 562 patients who completed colonic investigations, in addition to providing stool for FIT and FCP as well as urine samples for urinary VOC measurements, were included in the final outcome measures. RESULTS: The sensitivity and specificity for CRC using FIT was 0.80 [95% confidence interval (CI) 0.66-0.93] and 0.93 (CI 0.91-0.95), respectively. For urinary VOCs, the sensitivity and specificity for CRC was 0.63 (CI 0.46-0.79) and 0.63 (CI 0.59-0.67), respectively. However, for those who were FIT-negative CRC (i.e. false negatives), the addition of urinary VOCs resulted in a sensitivity of 0.97 (CI 0.90-1.0) and specificity of 0.72 (CI 0.68-0.76). CONCLUSIONS: When applied to the FIT-negative group, urinary VOCs improve CRC detection (sensitivity rises from 0.80 to 0.97), thus showing promise as a second-stage test to complement FIT in the detection of CRC.

Breathomics--exhaled volatile organic compound analysis to detect hepatic encephalopathy: a pilot study.

The current diagnostic challenge with diagnosing hepatic encephalopathy (HE) is identifying those with minimal HE as opposed to the more clinically apparent covert/overt HE. Rifaximin, is an effective therapy but earlier identification and treatment of HE could prevent liver disease progression and hospitalization. Our pilot study aimed to analyse breath samples of patients with different HE grades, and controls, using a portable electronic (e) nose. 42 patients were enrolled; 22 with HE and 20 controls. Bedside breath samples were captured and analysed using an uvFAIMS machine (portable e-nose). West Haven criteria applied and MELD scores calculated. We classify HE patients from controls with a sensitivity and specificity of 0.88 (0.73-0.95) and 0.68 (0.51-0.81) respectively, AUROC 0.84 (0.75-0.93). Minimal HE was distinguishable from covert/overt HE with sensitivity of 0.79 and specificity of 0.5, AUROC 0.71 (0.57-0.84). This pilot study has highlighted the potential of breathomics to identify VOCs signatures in HE patients for diagnostic purposes. Importantly this was performed utilizing a non-invasive, portable bedside device and holds potential for future early HE diagnosis.

The application of FAIMS gas analysis in medical diagnostics.

There is an ever increasing need to develop new tools to aid in the diagnosis and monitoring of human diseases. Such tools will ultimately reduce the cost of healthcare by identifying disease states more quickly and cheaply than current practices. One method showing promise is the analysis of gas-phase biomarkers from human breath, urine, sweat and stool that reflect bodily metabolism. Analysis of these volatiles by GC MS requires specialised infra-structure and staff, making it unsuitable for a clinical setting. Point of care sensor based technologies such as eNoses often suffer from stability and sensitivity issues. Field-Asymmetric Ion Mobility Spectrometry (FAIMS) has potential to fulfil this clinical need. In this paper we review the medical need, the technology, sampling methods and medical evidence thus far. We conclude with reflecting on future developmental steps necessary to bring the device into medical practice.

Development and application of a new electronic nose instrument for the detection of colorectal cancer.

Colorectal cancer is a leading cause of cancer death in the USA and Europe with symptoms that mimick other far more common lower gastrointestinal (GI) disorders. This difficulty in separating colorectal cancer from these other diseases has driven researchers to search for an effective, non-invasive screening technique. Current state-of-the-art method of Faecal Immunochemical Testing achieving sensitivity ~90%, unfortunately the take-up in the western world is low due to the low patient acceptability of stool samples. However, a wide range of cancers have been distinguished from each-other and healthy controls by detecting the gas/volatile content emanating patient biological media. Dysbiosis afforded by certain disease states may be expressed in the volatile content of urine - a reflection of the gut bacteria's metabolic processes. A new electronic nose instrument was developed at the University of Warwick to measure the gas/volatile content of urine headspace, based on an array of 13 commercial electro-chemical and optical sensors. An experimental setup was arranged for a cohort of 92 urine samples from patients of colorectal cancer (CRC), irritable bowel syndrome (IBS) and controls to be run through the machine. Features were extracted from response data and used in Linear Discriminant Analysis (LDA) plots, including a full 3-disease classification and one focussing on distinguishing CRC from IBS. The latter case was tested by the success of re-classification using an (n-1) K-nearest neighbour algorithm, showing 78% sensitivity and 79% specificity to CRC.

Review article: next generation diagnostic modalities in gastroenterology--gas phase volatile compound biomarker detection.

BACKGROUND: The detection of airborne gas phase biomarkers that emanate from biological samples like urine, breath and faeces may herald a new age of non-invasive diagnostics. These biomarkers may reflect status in health and disease and can be detected by humans and other animals, to some extent, but far more consistently with instruments. The continued advancement in micro and nanotechnology has produced a range of compact and sophisticated gas analysis sensors and sensor systems, focussed primarily towards environmental and security applications. These instruments are now increasingly adapted for use in clinical testing and with the discovery of new gas volatile compound biomarkers, lead naturally to a new era of non-invasive diagnostics. AIM: To review current sensor instruments like the electronic nose (e-nose) and ion mobility spectroscopy (IMS), existing technology like gas chromatography-mass spectroscopy (GC-MS) and their application in the detection of gas phase volatile compound biomarkers in medicine - focussing on gastroenterology. METHODS: A systematic search on Medline and Pubmed databases was performed to identify articles relevant to gas and volatile organic compounds. RESULTS: E-nose and IMS instruments achieve sensitivities and specificities ranging from 75 to 92% in differentiating between inflammatory bowel disease, bile acid diarrhoea and colon cancer from controls. For pulmonary disease, the sensitivities and specificities exceed 90% in differentiating between pulmonary malignancy, pneumonia and obstructive airways disease. These sensitivity levels also hold true for diabetes (92%) and bladder cancer (90%) when GC-MS is combined with an e-nose. CONCLUSIONS: The accurate reproducible sensing of volatile organic compounds (VOCs) using portable near-patient devices is a goal within reach for today's clinicians.

Evaluation of gut bacterial populations using an electronic e-nose and field asymmetric ion mobility spectrometry: further insights into 'fermentonomics'.

The fermentation of undigested foods in the large bowel, by its resident bacteria, results in the production of several chemicals including volatile gases. Perturbance in gut bacteria is known to influence colonic and metabolic health, but to determine this requires prolonged culture (often unsuccessful) or expensive genomic sequencing. Clearly this is not practical for daily clinical practice. Previously, we have reported our insights into fermentonomics through the detection of volatile organic compounds (VOCs) in patients with gastrointestinal and metabolic diseases, using the electronic nose. In this paper we report on the changes in the fermentone produced by patients undergoing complete versus partial bowel cleansing. Using urine samples, preliminary results from 23 individuals receiving bowel cleansing indicate the ability of the electronic nose to distinguish between the partial and complete procedures. Moreover in a subset of individuals, we have been able to track evolving bacterial recolonization over time using the e-nose and field asymmetric ion mobility spectrometry (FAIMS). Such an approach has practical application in tracking bacterial dysbiosis following perturbation.

Rapid manufacture of monolithic micro-actuated forceps inspired by echinoderm pedicellariae.

The concept of biomimetics and bioinspiration has been used to enhance the function of materials and devices in fields ranging from healthcare to renewable energy. By developing advanced design and manufacturing processes, researchers are rapidly accelerating their ability to mimic natural systems. In this paper we show how micro-actuated forceps inspired by echinoderm pedicellarie have been produced using the rapid manufacturing technology of micro-stereolithography. The manufactured monolithic devices are composed of sets of jaws on the surface of thin polymer resin membranes, which serve as musculature for the jaws. The membranes are suspended above a pneumatic chamber with the jaws opened and closed through pneumatic pressure changes exerted by a simple syringe. The forceps can be used for tasks such as grasping of microparticles. Furthermore, when an object is placed in the centre of the membrane, the membrane flexes and the jaws of the device close and grasp the object in a responsive manner. When uncured liquid photopolymer is used to actuate the devices hydraulically instead of pneumatically, the devices exhibit self-healing behaviour, sealing the damaged regions and maintaining hydraulic integrity. The manufactured devices present exciting possibilities in fields such as micromanipulation and micro-robotics for healthcare.

Mimicking the biological olfactory system: a Portable electronic Mucosa.

In this study the authors report on the development of a new type of electronic nose (e-nose) instrument, which the authors refer to as the Portable electronic Mucosa (PeM) as a continuation of previous research. It is designed to mimic the human nose by taking significant biological features and replicating them electronically. The term electronic mucosa or simply e-mucosa was used because our e-nose emulates the nasal chromatographic effect discovered in the olfactory epithelium, located within the upper turbinate. The e-mucosa generates spatio-temporal information that the authors believe could lead to improved odour discrimination. The PeM comprises three large sensor arrays each containing a total of 576 sensors, with 24 different coatings, to increase the odour selectivity. The nasal chromatographic effect provides temporal information in the human olfactory system, and is mimicked here using two-coated retentive channels. These channels are coated with polar and non-polar compounds to enhance the selectivity of the instrument. Thus, for an unknown sample, the authors have both the spatial information (as with a traditional e-nose) and the temporal information. The authors believe that this PeM may offer a way forward in developing a new range of low-cost e-noses with superior odour specificity.

Insights into 'fermentonomics': evaluation of volatile organic compounds (VOCs) in human disease using an electronic 'e-nose'.

Detection of volatile organic compounds (VOCs) is a common requirement in industry for which numerous methods are available. The electronic nose (e-nose) is an example. Rather than individual chemicals, the e-nose recognizes the 'aroma fingerprint' created by the collection of VOCs in samples, comparable to the human nose. We report on a novel application for gastrointestinal and metabolic medicine, and compare its results to mass spectrometry. Fermentation of undigested foods in the large bowel by its resident bacteria results in the creation of several chemicals including volatile gases that influence colonic and metabolic health. Using urine samples, preliminary results indicate the ability of the e-nose to distinguish between controls and those with inflammatory bowel disease or diabetes (separation rate of ∼97%). This emphasizes the different patterns of fermentation. Our term 'fermentonomics' describes the investigation and analysis of the fermentome by such non-invasive means. Such an approach has potentially wide application in medicine.

Towards a truly biomimetic olfactory microsystem: an artificial olfactory mucosa.

Today, the capability of the human olfactory system is still, in many ways, superior to that of the electronic nose. Although electronic noses are often compared with their biological counterpart, they neither mimic its neural architecture nor achieve its discriminating performance. Experimental studies on the mammalian olfactory system suggest that the nasal cavity, comprising of the mucous layer and the olfactory epithelium, performs a degree of chromatographic separation of complex mixtures. Thus receptor cells distributed beneath the mucous layer provide both spatial and temporal chemosensory information. Here we report on the development of an artificial olfactory microsystem that replicates this basic structure. This contains an integrated channel to emulate the nasal cavity and coated with a polymer to mimic the partitioning mucous layer, which is positioned directly over a sensor array. Our system employs an 80 element chemoresistive microsensor array with carbon black/polymer odour-sensitive films combined with a microfluidic package fabricated by micro-stereolithography. Results show that this biomimetic system generates both spatial and temporal odorant signals, with a temporal chemical retention period of up to 170 s. Data analysis has revealed improvements in its ability to discriminate between two simple odours and a set of complex odours. We believe such emulation of the olfactory system can lead to improved odour discrimination within the field of electronic noses.

Fournier gangrene associated with Crohn disease.

A 17-year-old boy presented with Fournier gangrene associated with previously undiagnosed Crohn ileocolitis. Fournier gangrene was managed by débridement, broad-spectrum antibiotics, and hyperbaric oxygen. A diverting ileostomy was performed before skin grafting and scrotal reconstruction. Microscopy of a full-layer surgical sample from the terminal ileum revealed granulomas with multinucleated histiocytes, consistent with Crohn disease. Crohn disease was treated with mesalamine, metronidazole, 6-mercaptopurine, and infliximab. The patient was discharged on hospital day 32. At 6-month follow-up, reconstruction of his scrotum had completely healed. Ostomy output was normal.