How variable are hydroxyproline determinations made in different samples of the same liver?

Abstract

Objectives: The haphazard distribution of fibrous tissue can interfere with quantitative methods for evaluating hepatic fibrosis. Inter-sample variation may represent a crucial issue when hydroxyproline measurement is used to quantify fibrosis. A comparative study of the hydroxyproline levels in normal and fibrotic rats is herein reported.

Material and methods: Twelve normal and 20 Capillaria hepatica-infected Wistar rats were used. Two fragments of the liver (A and B) of each rat were taken from separate areas and hydroxyproline measurements were made. Calculated differences in hydroxyproline measurements between samples from the same liver were analyzed by BOOTSTRAP.

Results: Differences in normal rats varied from 0.026 to 1.85 μmol of HP/g, in ten rats, the difference was less than 0.50 μmol. In infected rats, it varied from 0.04 to 2.86 μmol HP/g. Differences higher than 0.69 μmol/g were significant for normal rats (p < 0.05) and above 1.22 μmol/g (p < 0.05) for fibrotic rats.

Conclusions: Hydroxyproline ratio in a normal liver kept a fair degree of reproducibility. In the presence of hepatic fibrosis, the levels of hydroxyproline may vary significantly between samples from a single liver and may have limited value in quantifying the extent of fibrosis.