Automated method for measuring L-asparaginase activity

The main goal of L-asparaginase therapy in acute lymphoblastic leukemia (ALL) is complete depletion of asparagine in the blood and cerebrospinal fluid, accompanied by the death of tumor blasts. Asparagine is difficult to measure reliably due to its rapid degradation ex vivo. Serum asparaginase activity correlates well with asparagine depletion. International guidelines clearly state the need for therapeutic drug monitoring (TDM) of asparaginase activity in the blood to improve clinical outcomes in the treatment of patients with ALL. The aim of the article is to describe the adaptation of the method for measuring asparaginase activity in blood serum on a modern biochemical analyzer for use in everyday clinical practice of TDM. Materials and methods. Asparaginase activity was determined using the method of coupled enzymatic reactions accompanied by oxidation of reduced β-nicotinamide adenine dinucleotide (NADH) and a decrease in absorption at a wavelength of 340 nm. The rate of absorption decrease is proportional to the asparaginase activity in the test sample. All measurements were performed on an automatic biochemical analyzer AU 480 (Beckman Coulter). Results of the method adaptation for measurements on an automatic biochemical analyzer: limit of detection (LoD)=7.3 IU/L, lower limit of quantification (LoQ)=13.0 IU/L. Intra-assay precision was 2.1 and 0.97%, respectively, for control samples with an activity of 81.6 and 571.4 IU/L. Inter-assay precision for these control sera was 6.4 and 5.5%, respectively. Conclusion. The analytical characteristics of the method meet the requirements for bioanalytical methods and are close to those established in the work that we took as a basis for adaptation. The automated method allows for the full implementation of real-time TDM of asparaginase in patients with ALL.