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

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.