An LC-MS/MS method for creatine and creatinine analysis in paraquat-intoxicated patients

Abstract

A sudden increase in serum creatinine after paraquat intoxication has been reported in several clinical studies. However, this dramatic change of creatinine may be possibly due to an interconversion of creatine-creatinine in relation to paraquat toxicity. In order to investigate the creatine-creatinine relationship, a liquid chromatography tandem mass spectrometry in combination with electrospray ionization was developed and validated for simultaneous determination of creatine and creatinine in the serum. The chromatographic separation was achieved on a Gemini® C₆-Phenyl column with a gradient elution consisting of 0.1% formic acid in ultrapure water and methanol as the mobile phase. The method yielded suitable levels of specificity and selectivity, and calibration curves of creatine and creatinine in serum were linear over the concentration range of 0.5–200 µg mL⁻¹. The limit of quantification of both compounds was 0.5 µg mL⁻¹, and the method was accurate within the recovery range of 96.23–102.75%, indicating the robustness of the method. The method was successfully applied to toxicological samples from paraquat-intoxicated patients, and the concentrations of creatine and creatinine were quantified. High creatine concentrations in serum samples were observed which may lead to high serum creatinine despite normal kidney function as creatine is converted to creatinine in proportion to its concentration.

Keywords:

• Liquid chromatography tandem mass spectrometry
• creatine
• creatinine
• paraquat
• poisoning
• method validation
• method comparison
• matrix effect
• acute kidney injury
• kidney function
• nephrotoxicity

Acknowledgments

Funding body had no role in the design and execution of this study or interpretation of the data or decision to submit the manuscript. The authors are grateful to Mr. Pittaya Jaikwang for the preparation of Figure 1, Dr. Dale E. Taneyhill for proofreading the English, Mrs. Rochana Phuackchantuck for statistical supports, and SACTRC team for arranging sample shipment to Thailand.

Author contributions

KW and AJ conceived and designed the analysis. MS, AJ, and KW performed the analysis. FM and NB assisted with specimen collection. MS, KW, and AJ analyzed and interpreted the data. FM, NB, and KW contributed reagents/materials/analysis tools. KW and MS wrote the manuscript in consultation with FM, NB, and AJ.

Additional information

Funding

This work was supported by the Faculty of Medicine Research Fund, Faculty of Medicine, Chiang Mai University, Thailand Grant number 018/2561; and the NHMRC project Grant number 1011772.