FibroScan Report: kPa Stiffness and CAP Fat Reading Explained
A FibroScan report gives two numbers: liver stiffness in kPa, a clue to scarring, and CAP, a clue to fat. Neither one is a verdict on its own, and the reliability lines under them decide how much weight each number deserves.
At a glance
- Stiffness (kPa): a higher number means stiffer liver tissue, which can reflect scarring. The cut-off that matters depends on the cause of the liver disease.
- CAP (dB/m): a higher number points to more fat. The EASL 2021 summary cites 275 dB/m as a cut-off for detecting steatosis.
- Reliability lines: the count of valid readings, the success rate and the IQR/median ratio show whether the scan is trustworthy.
- Rule of thumb: one FibroScan number is a clue, and the reliability lines tell you how much to trust it.
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What does the kPa number on a FibroScan measure?
The probe sends a gentle pulse through the liver and measures how stiff the tissue is, reported in kilopascals (kPa). Doctors call this the liver stiffness measurement, or LSM. It is one of the non-invasive tests used to judge how severe a liver disease is and what the outlook may be, which is why it sits alongside blood tests and your history rather than replacing them.
Stiffness tells you nothing about fat. That is the job of the CAP line on the same printout, so a high kPa with a normal CAP points to a question about scarring, not fat.
Which kPa numbers count as high?
There is no single ladder that fits every liver. The EASL 2021 update, as summarised by Archer and colleagues in 2022, sets cut-offs by the disease behind the scan. The table shows the figures that summary gives.
| Liver condition | Cut-off (kPa) | What the number can do |
|---|---|---|
| Fatty liver not caused by alcohol | Below 8 | Can rule out advanced fibrosis |
| Alcohol-related liver disease | 12 to 15 or more | Can rule in advanced fibrosis |
| Primary biliary cholangitis | 10 or more | Diagnostic of advanced fibrosis |
| Primary sclerosing cholangitis | 9.5 or more | Indicates advanced fibrosis if bilirubin is normal |
Treat each row as a rule for one disease, not a grade you can copy across. A reading well below the line is reassuring, a reading above it is a reason to look further, and anything in the middle is a case for the doctor to combine with blood tests. Ask the clinic which cut-off their report uses, because the same number can mean different things under different rules.
What does the CAP reading tell you about fat?
CAP stands for controlled attenuation parameter, and it is reported in decibels per metre (dB/m). The EASL 2021 summary says a value above 275 dB/m has good sensitivity for detecting steatosis, the medical word for fat in the liver. The same summary says CAP’s role in measuring how much fat is present has been challenged, so read it as a clue about whether fat is there rather than a precise grade.
Which lines show that a scan is reliable?
- Count the valid readings. Fewer than 10 valid measurements is the traditional flag for an unreliable scan.
- Check the success rate. A success rate below 60% gets the same flag.
- Read the IQR/median ratio. A ratio above 30% is the traditional flag for a spread-out, shaky set of readings.
- Ask about a repeat if a line fails. Ask whether the centre would repeat the scan, and under what conditions, before you treat the number as final.
The flags were proposed by Castera and colleagues. A 2014 audit of 2,335 examinations applied them, and its authors pointed out that no study had shown the “unreliable” results to be less accurate. A failed line is therefore a reason to check and repeat, not proof that the number is wrong.
Why can a stiffness number read high when the liver is not badly scarred?
Several everyday factors push the number up, and none of them settles the question alone.
- A recent meal. In a 2017 study of 60 people, most with alcohol-related liver disease, liquid meals changed the readings. Transient elastography moved about 24% of people with F0 to F3 fibrosis into a higher stage after a moderate meal, and 54% after a high-calorie meal. The authors recommended more than three hours of fasting before the scan.
- Heart failure. Liver congestion, meaning blood and fluid backing up in the liver, can raise the reading. A 2022 review in ESC Heart Failure notes that a single value cannot tell reversible congestion from irreversible fibrosis, and that stiffness usually falls after diuresis, the medical term for fluid removal.
- Ongoing alcohol. The EASL summary links ongoing alcohol use with false-positive readings. It suggests repeating the scan a week after cutting back, when the reading is raised and AST or GGT is more than twice the upper limit of normal.
- Inflammation. Stiffness moves with inflammation too. In hepatitis C, a reading can fall as inflammation improves without showing that scarring has gone.
What should you do if the number is high?
Before the scan
Ask the centre whether you need to fast and for how long, and write down the time of your last meal on the request form. A clear note helps the reader judge the result. Local sheets differ, so follow the one you were given.
If the number comes back high, tell the doctor what you ate beforehand, whether you drink alcohol, and whether you have a heart condition or swelling in the legs. Those details change how the reading is interpreted. Then ask whether a repeat scan under the same conditions is worth doing before anyone draws a conclusion from one number.
How does this scan fit with your other liver tests?
A FibroScan rarely stands alone. Enzyme lines show how the liver is behaving on a blood test, and the fat grade from ultrasound describes what the scan saw. For the enzymes, read the SGPT high line by line guide. For ultrasound grades, see fatty liver grade 1, 2 and 3. For food and which tests to ask for, see fatty liver and desi food, and for the ALP and GGT lines, see the ALP and GGT report guide.
More report guides sit in the Lab Reports Decoded hub. If weight is part of the picture, the Desi Weight Loss section covers food and movement, and any new eating or exercise plan should be checked with your doctor first.
Never stop, start or change a medicine because of a scan number; the treating doctor decides what the report means for you. See a doctor promptly if the scan is high and you also have yellow skin or eyes, a swollen belly, black stools, vomiting blood or new confusion. If you have diabetes, kidney disease, heart disease or are pregnant, check any food or exercise change with your doctor first.
FibroScan report questions, answered
What is a normal FibroScan reading?
There is no single normal number for every liver. The EASL 2021 summary sets cut-offs by disease: below 8 kPa can rule out advanced fibrosis in fatty liver not caused by alcohol, and 12 to 15 kPa or more can rule it in for alcohol-related disease.
Is a FibroScan reliable?
It is a useful tool, but a single scan can be unreliable. Fewer than 10 valid readings, a success rate under 60% or an IQR/median ratio over 30% are the traditional flags to check.
What does CAP mean on a FibroScan report?
CAP is the fat reading, given in dB/m. The EASL 2021 summary cites a value above 275 dB/m as a sensitive cut-off for detecting steatosis.
Can eating before a FibroScan change the result?
Yes, a meal can raise the number. A 2017 study recommended more than three hours of fasting before liver stiffness readings.
What does IQR mean on a FibroScan report?
IQR is the spread of the valid readings. The IQR divided by the median is the ratio that flags an uneven scan, and above 30% is the traditional unreliable line.
Does a high FibroScan reading mean cirrhosis?
Not on its own. A high value is a reason for the doctor to look further, and the cut-off depends on the disease, while alcohol, inflammation or heart congestion can all raise the number.
Can heart failure affect FibroScan results?
Yes. Liver congestion from heart failure can raise the reading, and a single value cannot separate congestion from fibrosis, so the doctor may compare readings over time.
Does drinking alcohol affect a FibroScan?
Ongoing alcohol use is linked to false-positive readings. The EASL summary suggests repeating the scan about a week after cutting back, when the reading is raised and AST or GGT is more than twice the upper limit of normal.
Should I stop my medicine if the FibroScan is high?
No. Never stop or change a medicine because of a scan number. Take the report to your doctor, who decides what it means and what happens next.
Sources
- Journal of Hepatology (EASL): EASL Clinical Practice Guidelines on non-invasive tests for evaluation of liver disease severity and prognosis, 2021 update
- Frontline Gastroenterology (BMJ): Archer et al., EASL clinical practice guidelines: non-invasive liver tests (2022)
- Canadian Journal of Gastroenterology and Hepatology: Pang et al., The feasibility and reliability of transient elastography using Fibroscan: a practice audit of 2335 examinations (2014)
- PLoS One: High risk of misinterpreting liver and spleen stiffness using 2D shear-wave and transient elastography after a moderate or high calorie meal (2017)
- ESC Heart Failure: Use of liver stiffness measurements in acute decompensated heart failure (2022)