Ideal Setting for Performing a FibroScan
FibroScan should be performed in an outpatient setting with the patient fasting for at least 4 hours, positioned supine with the right arm maximally raised above the head, using the appropriate probe (M-probe for skin-liver capsule distance <25mm or BMI <32 kg/m², XL-probe for distance ≥25mm or BMI ≥32 kg/m²), obtaining at least 10 valid measurements with an interquartile range/median ratio <0.30 and ≥60% success rate. 1
Patient Preparation
- Fasting requirement: Patients must fast for at least 4 hours before the examination, as food intake increases hepatic blood flow and can artificially elevate liver stiffness values 1
- Light meals (≤300 kcal) have minimal impact on measurements in lean adults, but the 4-hour fasting recommendation remains standard practice 2
Patient Positioning
- Supine position with the right arm raised as high as possible above the head 1
- The probe is positioned perpendicularly on the skin surface between the right ribs at the liver location 1
- Measurements target the liver parenchyma while avoiding blood vessels 1
Probe Selection
Critical for accurate results, as M and XL probes yield significantly different values in the same patient 3:
- M-probe: Use when skin-liver capsule distance (SCD) is <25mm, typically in patients with BMI <32 kg/m² 3
- XL-probe: Use when SCD is ≥25mm, typically in patients with BMI ≥32 kg/m² 3
- S-probe: Reserved for children <18 years with thoracic circumference 45-75 cm 2, 4
- The FibroScan Automatic Probe Selection tool should guide probe choice based on BMI first, then SCD 3
Measurement Quality Criteria
All three validity criteria must be met for reliable results 5:
- ≥10 successful liver stiffness measurements obtained 1, 5
- Interquartile range/median (IQR/Med) ratio <0.30 5
- ≥60% measurement success rate 5
The median value of valid measurements is used for clinical interpretation 1
Clinical Setting Requirements
- Outpatient or community settings are appropriate, as the examination is rapid (takes <10 minutes) 6
- Can be performed at bedside in ambulatory office settings 7
- Medical, nursing, and other healthcare personnel can be easily trained to perform FibroScan 6
- Minimal operator training required: Operators achieve 64.7% validity by their 50th examination, with greatest improvement in the first 10 scans 5
Contraindications and Limitations
Avoid FibroScan in these situations 1:
- Ascites: Elastic waves cannot reach liver parenchyma 1
- Narrow intercostal space: Difficult probe positioning 1
- Pregnancy: Not recommended due to liver position changes 1
- Acute hepatitis, recent alcohol use, or cholestasis: These conditions artificially elevate liver stiffness independent of fibrosis 7, 8
Technical limitations include unreliable results in patients with BMI >28 kg/m² (though lower failure rates occur in Asian populations at 1.1-3.5% versus 4.3-7.0% in Western populations) 1
Important Caveats
- Probe-specific values differ: XL probe results are significantly lower than M probe results in the same patient (median 7.9 vs 9.5 kPa), making correct probe selection essential 3
- Sedation/anesthesia significantly increases liver stiffness measurements (5.4 vs 4.2 kPa in healthy children), confounding results 4
- Inflammation, congestion, and cholestasis affect liver stiffness measurements beyond fibrosis alone 8
- The examination measures a liver volume >100 times larger than liver biopsy, providing better sampling 1