kPa, CAP, UAP Demystified

Elastography vendors use different parameters and naming. Here’s how to compare them carefully.

What is kPa?

Liver stiffness is reported in kilopascals (kPa). It correlates with fibrosis stage, but can be elevated by inflammation, congestion, or cholestasis.

CAP vs. UAP

• CAP (Controlled Attenuation Parameter) — FibroScan’s steatosis estimate in dB/m.
• UAP/ATI — Ultrasound attenuation metrics from US vendors; scales differ (e.g., dB/cm/MHz).

Cross-Device Considerations

• Probe selection (M vs XL) alters reference cutoffs.
• Measurement window and ROI placement differ across systems.
• Population (NAFLD/NASH, viral hepatitis, cholestatic disease) affects thresholds.

Reporting Best Practices

• Always include device, probe, success rate, IQR/median.
• Note fasting status and confounders (ALT flare, CHF, cholestasis).
• Provide ranges as guidance, not absolute diagnosis.

How FibroAI Helps

We normalize terminology, cite etiology-specific ranges, and generate clear conclusions for clinicians and patients.