A matrix-induced ion suppression method to normalize concentration in urinary metabolomics studies using flow injection analysis electrospray ionization mass spectrometry.
Normalizing the total urine concentration is important for minimizing bias in urinary metabolomics analysis comparisons. In this study, we report a matrix-induced ion suppression (MIIS)-based method to normalize concentration using flow injection analysis coupled with electrospray ionization mass spectrometry (FIA-ESI-MS). An ion suppression indicator (ISI) was spiked into urine samples, and the intensity of the extracted ion chromatogram (EIC) for ISI in a urine matrix was subtracted by the EIC for a blank solution and used to calculate the extent to which the signal was reduced by the urine matrix. A series dilution of pooled urine samples was used to correlate the urine concentration and level of ion suppression for ISI. A regression equation was used to estimate the relative concentration of unknown urine samples. The MIIS method was validated for linearity, precision and accuracy. We obtained a good correlation using a quadratic regression model for 1- to 32-fold urine dilutions (R(2)=0.998). The reproducibility (n=4) and intermediate precision (n=3) were below 5% RSD, and the accuracy ranged from 97.15% to 102.10%. The established method was used to estimate the relative concentrations of 16 urine samples, and the results were compared with commonly used normalization methods. Pearson's correlation test was used to demonstrate that the MIIS method correlated highly with the creatinine and osmolarity methods; the correlation coefficients were 0.93 and 0.99, respectively. We successfully applied this method to a urinary metabolomics study on breast cancer. This study demonstrated the MIIS method is simple, accurate and can contribute to data integrity in urinary metabolomics studies.
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan; The Metabolomics Core Laboratory, Center of Genomic Medicine, National Taiwan University, Taipei, Taiwan.
Guan-yuan
GY
Chen
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan; The Metabolomics Core Laboratory, Center of Genomic Medicine, National Taiwan University, Taipei, Taiwan.
Hsiao-wei
HW
Liao
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan; The Metabolomics Core Laboratory, Center of Genomic Medicine, National Taiwan University, Taipei, Taiwan; Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan; Department of Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan.
Yufeng Jane
YJ
Tseng
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan; The Metabolomics Core Laboratory, Center of Genomic Medicine, National Taiwan University, Taipei, Taiwan.
I-lin
IL
Tsai
School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan; The Metabolomics Core Laboratory, Center of Genomic Medicine, National Taiwan University, Taipei, Taiwan; Department of Pharmacy, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: kuoch@ntu.edu.tw.
Ching-hua
CH
Kuo
D001943:Breast Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D003404:Creatinine / Q000378:metabolism / Q000652:urine*; D005260:Female; D017022:Flow Injection Analysis; D006801:Humans; D021241:Spectrometry, Mass, Electrospray Ionization
D003404:Creatinine
Breast cancer; Flow injection analysis-electrospray ionization-mass spectrometry; Matrix-induced ion suppression; Normalization; Urinary metabolomics