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Fibroscan
Is Fibroscan available in the US now? If so, where? Thanks for the help!
The gold standard for detecting liver fibrosis remains percutaneous liver biopsy, although this procedure is not without its own inherent limitations. These include (1) a small but significant risk for procedure-related complications such as pain or bleeding, (2) inaccurate staging from sampling error in up to 25% of cases, and (3) inter- and intraobserver variability in biopsy interpretation.3, 4 Because of these reasons and wide availability of serum diagnostic tests, the use of diagnostic liver biopsy in clinical practice is declining.5
From a clinical perspective, the greatest limitation with liver biopsy is sampling variability and its effect on fibrosis staging. Several investigations have documented that sampling error is present in a variety of liver diseases.6, 7 Furthermore, the performance of biopsies involving the right and left liver lobes in the same patient does not reduce sampling error, because substantial discordance in fibrosis stage is observed.7 Although the optimal liver biopsy specimen characteristics (≥20 mm in length with ≥11 portal tracts) have been identified to minimize the effects from sampling error,8 the typical specimen obtained in clinical practice often fails to meet these standards.
Ultrasound-Based TE.
This imaging modality uses a transducer probe which emits low-frequency (50 Hz) vibrations into the liver for measuring liver stiffness. The examination is performed over the right lateral intercostal spaces with the patient lying in the dorsal decubitus position and the right arm being in maximal abduction. The propagating shear wave induced by these vibrations is detected by a pulse-echo acquisition, and the velocity of the wave is then calculated. Liver stiffness is proportional to shear wave velocity as expressed by the equation for Young's modulus (expressed as E = 3pv2, where v is the shear velocity and p is the density of tissue, assumed to be constant). Liver stiffness is measured in kilopascals. Requirements for accurate TE measurement of mean liver stiffness include (1) an interquartile range for measurements within 30% of the median value and (2) a ratio of successful measurements to the total number of acquisitions ≥60%.11
In two meta-analyses,12, 13 the pooled estimates for the diagnosis of cirrhosis with TE were excellent, with sensitivity and specificity values approaching 90%. Reported diagnostic threshold (or cutoff) values for cirrhosis have ranged between 11 and 17 kPa in studies of patients with chronic hepatitis C. Results of TE from studies in other etiologies of liver disease such as chronic hepatitis B, alcohol, and nonalcoholic fatty liver disease are emerging. Despite its excellent accuracy for detecting cirrhosis, liver stiffness is an insensitive predictor for esophageal varices and should not dictate which patients should or should not be screened for esophageal varices by endoscopy.14 For the detection of hepatic fibrosis between stages 2-4, however, the pooled estimates of sensitivity and specificity are reduced to between 70% and 80%.12, 13
Magnetic Resonance Elastography.
MRE uses a modified phase-contrast imaging sequence to detect propagating shear waves within the liver. Acoustic shear waves are generated by a pneumatic driver placed directly over the upper abdomen for propagation into liver tissue. Subsequently, liver stiffness values are calculated from wave displacement patterns displayed as color-encoded images (elastograms). Region-of-interest analysis throughout four cross-sectional slices of liver (avoiding vascular structures) is then performed to calculate mean liver stiffness.15 Elasticity quantification by MRE is based on the formula representing shear modulus, which is equivalent to one-third of the Young's modulus used with TE.
Initial prospective studies have demonstrated the feasibility and diagnostic accuracy in detecting hepatic fibrosis with MRE. As with TE, the detection of cirrhosis by MRE is highly accurate with sensitivity and specificity values exceeding 90%, respectively. In contrast to TE, however, studies of MRE to date identify a higher diagnostic accuracy for detecting intermediate to severe fibrosis (F2-F4) with sensitivity and specificity values each in the 80%-85% range.16, 17
Although the reproducibility of TE is excellent within experienced centers, its accuracy is diminished when obesity and narrow rib interspaces are encountered.18 In a recent 5-year prospective study with 13,369 examinations, the probability of technical failure or generation of invalid results was independently associated with a body mass index > 30 kg/m2.19 The development of a specialized probe for obese patients may reduce the frequency of technically limited examinations in the future. The reproducibility of MRE is also excellent,20 yet reliance on individual operators does not exist, because imaging processes are essentially automated. Furthermore, MRE is not significantly affected by obesity or rib interspace width.
For both MRE and TE, it should also be noted that other pathophysiological processes including severe inflammation, cholestasis, and hepatic congestion may independently contribute to liver stiffness.12, 13, 18
From a clinical perspective, the greatest limitation with liver biopsy is sampling variability and its effect on fibrosis staging. Several investigations have documented that sampling error is present in a variety of liver diseases.6, 7 Furthermore, the performance of biopsies involving the right and left liver lobes in the same patient does not reduce sampling error, because substantial discordance in fibrosis stage is observed.7 Although the optimal liver biopsy specimen characteristics (≥20 mm in length with ≥11 portal tracts) have been identified to minimize the effects from sampling error,8 the typical specimen obtained in clinical practice often fails to meet these standards.
Ultrasound-Based TE.
This imaging modality uses a transducer probe which emits low-frequency (50 Hz) vibrations into the liver for measuring liver stiffness. The examination is performed over the right lateral intercostal spaces with the patient lying in the dorsal decubitus position and the right arm being in maximal abduction. The propagating shear wave induced by these vibrations is detected by a pulse-echo acquisition, and the velocity of the wave is then calculated. Liver stiffness is proportional to shear wave velocity as expressed by the equation for Young's modulus (expressed as E = 3pv2, where v is the shear velocity and p is the density of tissue, assumed to be constant). Liver stiffness is measured in kilopascals. Requirements for accurate TE measurement of mean liver stiffness include (1) an interquartile range for measurements within 30% of the median value and (2) a ratio of successful measurements to the total number of acquisitions ≥60%.11
In two meta-analyses,12, 13 the pooled estimates for the diagnosis of cirrhosis with TE were excellent, with sensitivity and specificity values approaching 90%. Reported diagnostic threshold (or cutoff) values for cirrhosis have ranged between 11 and 17 kPa in studies of patients with chronic hepatitis C. Results of TE from studies in other etiologies of liver disease such as chronic hepatitis B, alcohol, and nonalcoholic fatty liver disease are emerging. Despite its excellent accuracy for detecting cirrhosis, liver stiffness is an insensitive predictor for esophageal varices and should not dictate which patients should or should not be screened for esophageal varices by endoscopy.14 For the detection of hepatic fibrosis between stages 2-4, however, the pooled estimates of sensitivity and specificity are reduced to between 70% and 80%.12, 13
Magnetic Resonance Elastography.
MRE uses a modified phase-contrast imaging sequence to detect propagating shear waves within the liver. Acoustic shear waves are generated by a pneumatic driver placed directly over the upper abdomen for propagation into liver tissue. Subsequently, liver stiffness values are calculated from wave displacement patterns displayed as color-encoded images (elastograms). Region-of-interest analysis throughout four cross-sectional slices of liver (avoiding vascular structures) is then performed to calculate mean liver stiffness.15 Elasticity quantification by MRE is based on the formula representing shear modulus, which is equivalent to one-third of the Young's modulus used with TE.
Initial prospective studies have demonstrated the feasibility and diagnostic accuracy in detecting hepatic fibrosis with MRE. As with TE, the detection of cirrhosis by MRE is highly accurate with sensitivity and specificity values exceeding 90%, respectively. In contrast to TE, however, studies of MRE to date identify a higher diagnostic accuracy for detecting intermediate to severe fibrosis (F2-F4) with sensitivity and specificity values each in the 80%-85% range.16, 17
Although the reproducibility of TE is excellent within experienced centers, its accuracy is diminished when obesity and narrow rib interspaces are encountered.18 In a recent 5-year prospective study with 13,369 examinations, the probability of technical failure or generation of invalid results was independently associated with a body mass index > 30 kg/m2.19 The development of a specialized probe for obese patients may reduce the frequency of technically limited examinations in the future. The reproducibility of MRE is also excellent,20 yet reliance on individual operators does not exist, because imaging processes are essentially automated. Furthermore, MRE is not significantly affected by obesity or rib interspace width.
For both MRE and TE, it should also be noted that other pathophysiological processes including severe inflammation, cholestasis, and hepatic congestion may independently contribute to liver stiffness.12, 13, 18
I'm not sure which states have fibroscan. Anyone who knows care to share? I'm also scared of doing biopsy. I just do ultrasound of whole abdomen. Thinking of traveling to a place with fibroscan to do it, after it's only once every 6 months.
1 Comments
UAB in Birmingham, Alabama has a Fibroscan.
I'm also thinking about Mayo's elastography. You have any idea how much they charge for this scan? Yes, getting insurance to send me to Mayo clinic will be a challenge. I also don't want to do liver biopsy.
It would be good to hear which states have it.
Biopsy I am kind of scared to do. I am just doing regular ultra sounds and low radiation CT scans of the abdomen with HIDA nuclear scan.
I know biopsy would be good to do also. But I am very reluctant doing this procedure.
And flying over to Mayo clinic is kinda far for me. I mean I could start writing books about US healthcare system with so many places I have been and so many clueless doctors about hbv that I have seen. It is a joke I will tell you. But things are somewhat improving with the healthcare reform taking place. But Hepatitis B treatment is really neglected. Hep C is good there is a treatment plan and they know what to give them. But for is just nucs and some people will do interferon and that is about it. Biopsy they like to do yes - the cost to insurance is about 7-$10‚000 for this procedure. And hospitals love it to.
Biopsy I am kind of scared to do. I am just doing regular ultra sounds and low radiation CT scans of the abdomen with HIDA nuclear scan.
I know biopsy would be good to do also. But I am very reluctant doing this procedure.
And flying over to Mayo clinic is kinda far for me. I mean I could start writing books about US healthcare system with so many places I have been and so many clueless doctors about hbv that I have seen. It is a joke I will tell you. But things are somewhat improving with the healthcare reform taking place. But Hepatitis B treatment is really neglected. Hep C is good there is a treatment plan and they know what to give them. But for is just nucs and some people will do interferon and that is about it. Biopsy they like to do yes - the cost to insurance is about 7-$10‚000 for this procedure. And hospitals love it to.
What I have heard that Sloan -Kattering cancer center has it. And Mayo clinic has their own version which is called elastography. Which is the same thing but done on a CT like machine.
But the rest of the places here are in the dark. They dont care here about HBV treatment. Even Dr.Gish team does not care for these tests. No surface antigen quantitative or fibroscan for us. And getting insurance send you to Mayo clinic will be a challenge.
But the rest of the places here are in the dark. They dont care here about HBV treatment. Even Dr.Gish team does not care for these tests. No surface antigen quantitative or fibroscan for us. And getting insurance send you to Mayo clinic will be a challenge.
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