Non-Invasive Distinction of Non-Alcoholic Fatty Liver Disease using Urinary Volatile Organic Compound Analysis: Early Results

Abstract

Background & Aims: Non-Alcoholic Fatty Liver Disease (NAFLD) is the commonest cause of chronic liver disease in the western world. Current diagnostic methods including Fibroscan have limitations, thus there is a need for more robust non-invasive screening methods. The gut microbiome is altered in several gastrointestinal and hepatic disorders resulting in altered, unique gut fermentation patterns, detectable by analysis of volatile organic compounds (VOCs) in urine, breath and faeces. We performed a proof of principle pilot study to determine if progressive fatty liver disease produced an altered urinary VOC pattern; specifically NAFLD and Non-Alcoholic Steatohepatitis (NASH).Methods: 34 patients were recruited: 8 NASH cirrhotics (NASH-C); 7 non-cirrhotic NASH; 4 NAFLD and 15 controls. Urine was collected and stored frozen. For assay, the samples were defrosted and aliquoted into vials, which were heated to 40±0.1°C and the headspace analyzed by FAIMS (Field Asymmetric Ion Mobility Spectroscopy). A previously used data processing pipeline employing a Random Forrest classification algorithm and using a 10 fold cross validation method was applied.Results: Urinary VOC results demonstrated sensitivity of 0.58 (0.33 - 0.88), but specificity of 0.93 (0.68 - 1.00) and an Area Under Curve (AUC) 0.73 (0.55 -0.90) to distinguish between liver disease and controls. However, NASH/NASH-C was separated from the NAFLD/controls with a sensitivity of 0.73 (0.45 - 0.92), specificity of 0.79 (0.54 - 0.94) and AUC of 0.79 (0.64 - 0.95), respectively.Conclusions: This pilot study suggests that urinary VOCs detection may offer the potential for early non-invasive characterisation of liver disease using 'smell prints' to distinguish between NASH and NAFLD.

Faecal volatile organic compounds analysis using field asymmetric ion mobility spectrometry: non-invasive diagnostics in paediatric inflammatory bowel disease

“…Patient characteristics were similar in the three subgroups, except for sex, with a predominance for female in the UC subgroup, however, previous studies have shown that gender does not affect VOC composition. (23)(24)(25) In conclusion, we observed that faecal VOC analysis by FAIMS could discriminate paediatric de novo IBD patients from healthy controls, with modest accuracy. The apparently high specificity of faecal VOCs compared to faecal calprotectin underlines the potential of this method to serve as a complementary, non-invasive technique in the diagnosis of paediatric IBD, possibly limiting the needed number of endoscopies in a subset of children suspected for IBD.…”

“…The FAIMS data was processed using a well-established pipeline, which has been developed specifically for these types of studies and has previously been reported. [19,23,24] In brief, first a preprocessing step was applied to each run in the form of a 2D wavelet transform (using Daubechies D4 wavelets). This performs two tasks, first as a data compression step and secondly as it can aid in the selection of chemical species by extracting 'peaks', which results in concentrating the chemical information into a small number of wavelet coefficients.…”

Pre-analytical and analytical variables that influence urinary volatile organic compound measurements

“…Our group has extensively investigated the use of VOCs across a wide range of gastrointestinal and metabolic disorders, principally from urine samples [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It is our opinion that urine represents the most acceptable and user-friendly medium, for both patients and the investigating team.…”

Accurate non‐invasive diagnosis and staging of non‐alcoholic fatty liver disease using the urinary steroid metabolome

“…Untargeted urinary metabolic profiling in small numbers of patients has been explored, 18,19 but its diagnostic ability has not been interrogated in detail. Volatile organic compound generated via the gut microbiome and excreted in the urine have been examined in a very small exploratory pilot study with AUC ROC values of 0.73 (0.45‐0.92) to distinguish advanced disease 20 …”