Direct comparison of the FibroScan XL and M probes for assessment of liver fibrosis in obese and nonobese patients

Esteban Durango; Christian Dietrich; Helmut Karl Seitz; Cornelia Ursula Kunz; Gilles T Pomier-Layrargues; Andres Duarte-Rojo; Melanie Beaton; Magdy Elkhashab; Robert P Myers; Sebastian Mueller

doi:10.2147/HMER.S45234

Direct comparison of the FibroScan XL and M probes for assessment of liver fibrosis in obese and nonobese patients

Hepat Med. 2013 Jul 4:5:43-52. doi: 10.2147/HMER.S45234. eCollection 2013.

Affiliations

¹ Department of Medicine and Center for Alcohol Research, Liver Disease and Nutrition, Salem Medical Center, Germany.
² Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany.
³ Liver Unit, Centre Hospitalier de l'Université de Montréal, Hôpital Saint-Luc, Montréal, Quebec, Canada.
⁴ Toronto Western Hospital Liver Centre, Toronto, Ontario, Canada.
⁵ Multi-Organ Transplant Unit, University of Western Ontario, London, Ontario, Canada.
⁶ The Toronto Liver Centre, Toronto, Ontario, Canada.
⁷ Liver Unit, Division of Gastroenterology and Hepatology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
⁸ Department of Medicine and Center for Alcohol Research, Liver Disease and Nutrition, Salem Medical Center, Germany ; Liver Unit, Centre Hospitalier de l'Université de Montréal, Hôpital Saint-Luc, Montréal, Quebec, Canada.

Abstract

Background: A novel Fibroscan XL probe has recently been introduced and validated for obese patients, and has a diagnostic accuracy comparable with that of the standard M probe. The aim of this study was to analyze and understand the differences between these two probes in nonobese patients, to identify underlying causes for these differences, and to develop a practical algorithm to translate results for the XL probe to those for the M probe.

Methods and results: Both probes were directly compared first in copolymer phantoms of varying stiffness (4.8, 11, and 40 kPa) and then in 371 obese and nonobese patients (body mass index, range 17.2-72.4) from German (n = 129) and Canadian (n = 242) centers. Liver stiffness values for both probes correlated better in phantoms than in patients (r = 0.98 versus 0.82, P < 0.001). Significantly more patients could be measured successfully using the XL probe than the M probe (98.4% versus 85.2%, respectively, P < 0.001) while the M probe produced a smaller interquartile range (21% versus 32%). Failure of the M probe to measure liver stiffness was not only observed in patients with a high body mass index and long skin-liver capsule distance but also in some nonobese patients (n = 10) due to quenching of the signal from subcutaneous fat tissue. In contrast with the phantoms, the XL probe consistently produced approximately 20% lower liver stiffness values in humans compared with the M probe. A long skin-liver capsule distance and a high degree of steatosis were responsible for this discordance. Adjustment of cutoff values for the XL probe (<5.5, 5.5-7, 7-10, and >10 kPa for F0, F1-2, F3, and F4 fibrosis, respectively) significantly improved agreement between the two probes from r = 0.655 to 0.679.

Conclusion: Liver stiffness can be measured in significantly more obese and nonobese patients using the XL probe than the M probe. However, the XL probe is less accurate and adjusted cutoff values are required.

Keywords: M probe; XL probe; cirrhosis; liver fibrosis; liver stiffness; obesity; steatosis; transient elastography.