Technical validation and feasibility of video particle tracking for low-volume measurement of biliary micro-viscosity after liver transplantation

Abstract

Abstract Reliable quantification of the biophysical properties of human bile requires analytically validated methods and standardized pre-analytical conditions. We hypothesized that biliary micro-viscosity can be quantified in human bile after liver transplantation (LTx) with predefined analytical performance (accuracy $$\le 15\%$$ deviation from reference, reproducibility CV $$<10\%$$ ). In this method-development and technical-validation study, we established a method to quantify micro-viscosity in human bile after LTx. Validation using sucrose standards demonstrated high accuracy ( $$\le 15\%$$ deviation from reference), strong linear correlation ( $$\textrm{R}^2 = 0.996$$ ), and good reproducibility (CV $$<10\%$$ ). The method was applied to 21 bile samples from nine patients collected longitudinally after LTx. Mean micro-viscosity was $$1.58 \pm 0.54~\text {mPa s}$$ (postoperative day 1), $$1.94 \pm 0.63~\text {mPa s}$$ (day 7), and $$1.44 \pm 0.16~\text {mPa s}$$ (day 14). Pre-analytical freezing and cooling introduced measurement variability, supporting analysis shortly after collection. These findings demonstrate the analytical performance and practical feasibility of video particle-tracking-based biliary micro-viscosity measurements after LTx. Larger studies combining standardized fresh-sample workflows, biochemical bile characterization, and longitudinal clinical outcome data are required to determine the biological relevance of biliary micro-viscosity and its potential value for future graft modeling.