GC–MS for Measuring the Progression of Kidney Disease

In a recent study out of Shanghai, Beijing, and Guangzhou, China, scientists used gas chromatography–mass spectrometry (GC–MS) to test the potential of breath volatile organic compounds (VOCs) for measuring the progression of chronic kidney disease (CKD). Their findings were published in Analyst (1). Breath volatile organic compounds are gases emitted into the air from breathing, some of which can be harmful and others that react with other gases and form different types of air pollutants. Breathing in VOCs, which can stem from sources like disinfectants, tobacco smoke, adhesives, and gasoline, can damage the eyes, nose, and throat, cause breathing difficulties, and even potentially cause cancer (2).

Kidney stone human renal disease vector background | Image Credit: © Siberian Art - stock.adobe.com

Chronic kidney disease (CKD) occurs when the kidneys are damaged and cannot properly filter blood. This leads to excess fluid and waste from blood remaining in the body, potentially leading to other health problems, like heart disease and stroke (3). Approximately 37 million people in the U.S. are estimated to have chronic kidney disease; that is more than 1 in 7 people. If left untreated, CKD can lead to kidney failure and early cardiovascular disease. There is also a chance that the kidneys can stop working, which is known as end-stage renal disease (ESRD), leading to dialysis or a kidney transplant being needed for survival.

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Recently, it has been suggested that breath analysis could be a convenient and non-invasive method for clinically monitoring CKD progression. However, there is a lack of breath volatile organic compounds (VOCs) that could indicate the progression of CKD. To rectify this, the scientists in this study used gas chromatography–mass spectrometry (GC–MS) for the untargeted detection of breath VOCs in patients with stage 1, 3, and 5 CKD. Following the experiment, it was found that as CKD stages increased, the levels of the levels of breath 4-heptanone, n-octane, and n-dodecane gradually increased, enabling more reliable monitoring for CKD progression. Moreover, the increasing rates from CKD stage 3 to stage 5were higher than the rates from CKD stage 1 to stage 3. These rates were found to be unaffected by factors like gender, smoking habits, age, and body mass index (BMI), which had insignificant impact on the levels of the three breath VOCs.

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Two different models were used based on based on 4-heptanone, n-octane, and n-dodecane combination: polynomial support vector machine (SVM) and K-nearest neighbor (KNN). Their accuracies in distinguishing between CKD stages 1, 3, and 5 were 76.3% and 72.8%, respectively. Out of the different components, the combination of 4-heptanone, n-octane, and n-dodecane proved superior for monitoring CKD progression. Though there is more work to be done, the scientists believe their findings have valuable implications for bettering both long-term CKD clinical monitoring and our overall understanding of CKD.

References

(1) Li, L.; Wang, J.; Feng, F.; Yan, J.; Zhao, B.; Li, X.; Zhong, Y. Breath Volatile Organic Compounds for Chronic Kidney Disease Progression Monitoring. Analyst 2024, 4. DOI: https://doi.org/10.1039/D3AN01057K

(2) Volatile Organic Compounds. American Lung Association 2024. https://www.lung.org/clean-air/indoor-air/indoor-air-pollutants/volatile-organic compounds (accessed 2024-3-19)

(3) Chronic Kidney Disease Basics. U.S. Department of Health & Human Services 2024. https://www.cdc.gov/kidneydisease/basics.html (accessed 2024-3-19)