FEATURE HEPATOLOGY
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The 4th Middle East Gasteroenterology conference is taking place during Arab Health from 23rd
-24th of January. To
register to attend on-site, visit the Delegate Registration Zone desks in the Al Wasl Foyer, situated between halls 4 and 5.
In vivo phosphorus-31 (31 P) MRS
provides metabolic information, which is useful when assessing fibrogenesis. The PME/PDE ratio has been used as an index of cell membrane turnover and has been shown to correlate with disease severity, assessed by histology in chronic hepatitis C. MRS provided a sensitivity and specificity of 82% and 81% respectively for cirrhosis and showed statistically significant differences between mild hepatitis, moderate hepatitis and cirrhosis (see figure 3).
MRS IN HEPATIC STEATOSIS: In hepatic steatosis, proton (1
Water
Figure 4: 1
H MRS. Proton (1H) MR Spectra (left to right) from (i) a patient with significant
hepatic steatosis, (ii) a patient with mild hepatic steatosis; (iii) a healthy volunteer. The intrahepaticellular (IHCL) lipid resonance is many times larger in (i) than (iii), with the hepatic water resonance scaled to the same height for comparative purposes. ppm = parts per million; IHCL CH2 = intrahepatocellular lipid. Reproduced from Thomas et al. 2005.
IHCL CH2
H) MRS
can provide information on the amount of liver fat. More recent studies have demonstrated to the potential to measure lipid composition non-invasively, which may change with disease state and with dietary intervention. Typical hepatic spectra contain water, fat and choline resonances, which can be quantified using external reference standards or expressed in terms of a percentage, Recent longitudinal work in patients with chronic hepatitis C has demonstrated a change in the ratio of PME/ PDE in response to antiviral treatment, separating virological responders from non- responders relative to the total MR signal (see figure 4). 1
H MRS is readily accessible to all centres that have a MR scanner 7.0 5.0 3.0 ppm
and most machines have the capability to perform such sequences as an addition to a standard MRI examination.
THE FUTURE OF BIOMARKERS OF CHRONIC LIVER DISEASE Inflammation, steatosis, fibrosis and fibrogenesis are complex multistep processes. It would be surprising if a single biomarker were able to describe liver disease completely. Accordingly, combinations of markers and modalities may describe disease more accurately
Table 1 Examples of serum markers for the assessment of fibrosis
Name
Indirect markers APRI
FibroTest
Direct markers ELF
FibroSpect Constituents AST, platelets
a2 macroglobulin, a2 and g globulin, total bilirubin, apolipoprotein A1
, gGT PIIINP, HA, TIMP-1, (age) HA, TIMP-1, a2 macroglobulin
90.5 41 99 92 77 73 74 76
Abbreviations: APRI, aspartate aminotransferase (AST) to platelet ratio index; gGT, g-glutamyl transferase; HA, hyaluronic acid; PIIINP, amino terminal of procollagenase III; TIMP-1, tissue inhibitor of matrix metalloproteinase 1; ELF, Enhanced Liver Fibrosis test; Se, sensitivity; Sp, specificity; PPV, positive predictive value; NPV, negative predictive value.
Accuracy (%) Se Sp PPV NPV
41 95 88 64 87 59 63 85
and reproducibly than one marker alone. Studies of marker combinations should be performed to establish optimal combinations, in terms of numbers of tests, accuracy of combinations and the provision of complementary information from the test components. Candidate markers differ widely in the equipment and expertise required, so cost-benefit analyses compared to routine liver biopsy are warranted. Serum panel markers and other imaging techniques including ultrasound and magnetic resonance modalities need to be investigated longitudinally in response to intervention in a number of disease states. As histological assessment of liver biopsy is itself a surrogate marker of liver disease, the challenge is to develop and validate protocols correlated to clinically meaningful outcome measures. Further research into non-invasive technologies for the assessment of chronic liver disease is required to optimise these techniques, to correlate with clinical outcomes and to incorporate them into validated management algorithms. ■
AH
REFERENCES References available on request (
magazine@informa.com)
Arab Health Show Issue 2012 61 1.0 -1.0
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