Hepatology
Liver Fibrosis
Detecting Liver Fibrosis in the Morbidly Obese Patient
Overview
Serum-based tests to assess the risk of liver fibrosis may be performed regardless of obesity status. When these tests do not exclude the likelihood of advanced fibrosis, the next step may be vibration-controlled transient elastography (VCTE); however, technical challenges may arise with this technique in the setting of morbid obesity.
Expert Commentary
Ashwani K. Singal, MD, MS, AGAF, FACG, FAASLD
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“ . . . if the risk of fibrosis is a bit higher based on FIB-4 or NFS, or if it is in the indeterminant range, the next step in the pathway is often to obtain a VCTE. This is where technical difficulties may emerge with regard to measuring liver stiffness accurately in patients with morbid obesity; in fact, this is a frequent issue in clinical practice.”
One of the main challenges with noninvasive testing in patients with morbid obesity relates to limitations with VCTE (eg, FibroScan [Echosens]). Magnetic resonance elastography (MRE) has been shown to be more technically reliable than VCTE in this population.
The accuracy of noninvasive tests using serum markers is generally similar in patients with and without obesity. In a subgroup analysis from a study by Joo et al, the area under the receiver operating characteristic curves of the Fibrosis-4 (FIB-4) index and the nonalcoholic fatty liver disease fibrosis score (NFS) for predicting advanced fibrosis were significantly higher in the nonobese subgroup than in the obese subgroup. If you look a bit further, however, despite having low positive predictive values, both of these tests had high negative predictive values in the subset with obesity, in the range of what is observed in a population without obesity.
Therefore, in thinking about the primary care setting and the use of noninvasive testing, serum markers are quite effective if the aim is to exclude a population that has a low risk of fibrosis, and I believe that this is true regardless of whether the population has obesity.
However, if the risk of fibrosis is a bit higher based on FIB-4 or NFS, or if it is in the indeterminant range, the next step in the pathway is often to obtain a VCTE. This is where technical difficulties may emerge with regard to measuring liver stiffness accurately in patients with morbid obesity; in fact, this is a frequent issue in clinical practice. Even when using an XL probe, there may be problems with the actual measurement of liver stiffness in 10% to 20% of those with morbid obesity. Therefore, in this scenario, you might want to use other ways of testing these individuals, such as MRE or, perhaps, a liver biopsy, although there may also be issues with MRE (eg, size constraints of the magnet bore).
To summarize, one can still test with VCTE in a patient with morbid obesity if the initial serum biomarker assessment is indeterminant or does not exclude advanced fibrosis. If that is technically accurate and technically feasible, and the images are accurate, then one would not necessarily need to do anything differently to detect fibrosis than what one would do in a patient without obesity. However, if the VCTE measurement is not technically accurate or technically feasible, then one might use either MRE or a liver biopsy, the latter being the gold standard (albeit an invasive procedure).
References
Alizai PH, Lurje I, Kroh A, et al. Noninvasive evaluation of liver function in morbidly obese patients. Gastroenterol Res Pract. 2019;2019:4307462. doi:10.1155/2019/4307462
Alqahtani SA, Golabi P, Paik JM, et al. Performance of noninvasive liver fibrosis tests in morbidly obese patients with nonalcoholic fatty liver disease. Obes Surg. 2021;31(5):2002-2010. doi:10.1007/s11695-020-04996-1
Chen J, Yin M, Talwalkar JA, et al. Diagnostic performance of MR elastography and vibration-controlled transient elastography in the detection of hepatic fibrosis in patients with severe to morbid obesity. Radiology. 2017;283(2):418-428. doi:10.1148/radiol.2016160685
Eren F, Kaya E, Yilmaz Y. Accuracy of Fibrosis-4 index and non-alcoholic fatty liver disease fibrosis scores in metabolic (dysfunction) associated fatty liver disease according to body mass index: failure in the prediction of advanced fibrosis in lean and morbidly obese individuals. Eur J Gastroenterol Hepatol. 2022;34(1):98-103. doi:10.1097/MEG.0000000000001946
Harris R, Card TR, Delahooke T, Aithal GP, Guha IN. The XL probe: a luxury or a necessity? Risk stratification in an obese community cohort using transient elastography. United European Gastroenterol J. 2018;6(9):1372-1379. doi:10.1177/2050640618772944
Joo SK, Kim W, Kim D, et al. Steatosis severity affects the diagnostic performances of noninvasive fibrosis tests in nonalcoholic fatty liver disease. Liver Int. 2018;38(2):331-341. doi:10.1111/liv.13549
López IC, Aroca FG, Bernal MDF, et al. Utility of the ELF test for detecting steatohepatitis in morbid obese patients with suspicion of nonalcoholic fatty liver disease. Obes Surg. 2017;27(9):2347-2353. doi:10.1007/s11695-017-2606-9
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Perumpail BJ, Khan MA, Yoo ER, Cholankeril G, Kim D, Ahmed A. Clinical epidemiology and disease burden of nonalcoholic fatty liver disease. World J Gastroenterol. 2017;23(47):8263-8276. doi:10.3748/wjg.v23.i47.8263
Sanyal AJ, Shankar SS, Yates K, et al. Primary results of the NIMBLE stage 1-NASH CRN study of circulating biomarkers for nonalcoholic steatohepatitis and its activity and fibrosis stage [abstract LO1]. Abstract presented at: AASLD The Liver Meeting; November 12-15, 2021.
