# Validation and stability analysis of guanine deaminase assay kit

## TL;DR

This paper presents a new, stable, and sensitive assay kit for measuring guanine deaminase activity, which is important for liver function diagnosis.

## Contribution

A novel GD assay kit with high sensitivity and stability using a double enzyme-coupling method and composite stabilizers.

## Key findings

- The GD kit showed a reagent blank absorbance of <0.2 and a mean recovery rate of 103%.
- The kit had an inter-batch and intra-batch difference of <15% and a linear range of 0-50 U/L (R2 > 0.99).
- The kit remained stable for 12 months with no significant loss of enzymatic activity when using the composite stabilizers.

## Abstract

Guanine deaminase (GD)plays important roles in the diagnosis of liver function. However, there is no totally rapid and simple for the eatimation of GD activity in clinical application. Herein, we have constructed an enzymatic assay system with highly sensitive and strong stability for quantification of GD activity by highly double enzyme-coupling (xanthine oxidase and uric acid oxidase) and adding compound stabilizer in GD kit. In this study, we validated parameters, including reagent blank, sensitivity, accuracy, inter-batch difference, intra-batch difference, linear range. Furthermore, composite stabilizers, containing gentamicin sulfate, bovine serum albumin, and mannitol, were selected to improve stability of GD kit during long-term storage. The experimental results showed that the absorbance of the reagent blank was <0.2, the mean recovery rate was 103 %, the inter-batch and intra-batch diffeerence were <15 %, The linearity range was 0 U/L-50 U/L (R2 > 0.99). All indicators met the kit requirements for clinical applications. When gentamicin sulfate, bovine serum albumin, and mannitol were used as a stabilizer, the kit remained stable for 12 months without significant loss of enzymatic activity. These results indicated that GD kit possesses high sensitivity and strong stability, which can be used for routine biochemical applications and is of great significance for the diagnosis and differential diagnosis of liver diseases.