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Abstract: TH-PO033

Urine Mass Spectrometry Can Distinguish Prerenal and Intrarenal AKI

Session Information

Category: Acute Kidney Injury

  • 102 AKI: Clinical‚ Outcomes‚ and Trials

Authors

  • Mitchell, Reece Buchanan, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • James, Luke T., University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • Herzog, Christian, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • Holthoff, Joseph H., University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
  • Arthur, John M., University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
Background

Postrenal causes of acute kidney injury (AKI) are often determined by imaging, but differentiation of prerenal (PR) from intrinsic renal (IR) can be challenging. A point of care method for differentiating these two entities would be useful. Mass spectrometry (MS) can visualize small molecules in urine. We utilized a portable, single quadrupole mass spectrometer with a simple ionization interface to measure small molecules in urine. The interface allows for direct analysis of samples without the need for time-consuming preparation. The goal was to distinguish PR and IR AKI by urine analyte profiles.

Methods

Inpatients with AKI were eligible for enrollment. COVID-19 patients were excluded. Informed consent was obtained under an approved UAMS IRB protocol. Patients were categorized as either PR (n=15) or IR (n=19) AKI etiology using the diagnosis by the on-service nephrology attending. Two microliter aliquots of urine were dispensed onto a stainless steel probe without prior processing and analyzed by MS with an Advion Expression CMS Mass Spectrometer. Peaks were recorded within the 20 to 500 m/z range. MS spectra were processed and binned in 1 m/z increments for peak clustering using MATLAB. The frequency of binned peaks in the PR AKI group were compared to the IR group and marked as a PR peak of interest if the difference in peak occurrence was eight or more. IR peaks of interest were identified similarly.

Results

Fifteen peaks met our initial criteria for difference in frequency between intrinsic and prerenal cases. From the fifteen, two were PR peaks and thirteen were IR peaks of interest. Mann-Whitney-U testing identified two peaks of significant variation between the PR and IR population: a PR peak with a m/z of 233 (p=0.0027) and an IR peak with a m/z of 372 (p=0.0027).

Conclusion

Point of care MS has the potential to rapidly differentiate PR from IR and potentially to further phenotype causes of AKI. Based on previous studies, the peaks we identified are likely small molecule metabolites. Additional sampling will enable the use of machine learning algorithms to classify the kidney disease that is present. Further correlation of the different analytes in prerenal and intrarenal AKIs is needed, however this study shows the potential utility of mass spectrometry to rapidly phenotype AKI in the clinical setting.