Performance Evaluation of High-performance Liquid Chromatography Instrument in Determining the Serum Concentration of Linezolid

LM1010, a high-performance liquid chromatography system for therapeutic drug monitoring (TDM) of various agents in clinical practice, is currently approved in Japan. Unlike conventional systems, LM1010 can rapidly measure clinical samples, and data analysis is based on the absolute calibration curve method and fully automated. However, the analytical performance of the LM1010 for the measurement of serum concentrations of linezolid (LZD) has not yet been evaluated. In this study, we aimed to evaluate the analytical performance of LM1010 and confirm the long-term stability of LZD at -30°C. One hundred forty-eight serum samples were collected from 25 patients (17 men and 8 women) who received LZD. Serum concentrations of LZD were measured using LM1010 and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Three LM1010 instruments were used to confirm the differences in the measured values. A Passing-Bablok regression analysis demonstrated a strong correlation between LM1010 and LC-MS/MS (r=0.991), and comparable results were observed among the three LM1010 instruments (r=0.982-0.998). Bland-Altman analyses revealed that the average difference between LM1010 and LC-MS/MS methods was 1.7%, and similar results were observed among the three LM1010 instruments. The long-term stability of serum LZD in samples stored at -30°C for 48 weeks was also confirmed. These results suggest that LM1010 can be used for TDM of LZD in clinical practice.