Abstract: TH-PO128

An Automated Immunoassay for High-Throughput Measurement of Symmetric Dimethylarginine (SDMA) in Human Serum

Session Information

Category: Glomerular

  • 1004 Clinical/Diagnostic Renal Pathology and Lab Medicine

Authors

  • El-Khoury, Joe M., Yale University, New Haven, Connecticut, United States
  • Wilson, Parker C., Yale University, New Haven, Connecticut, United States
  • Toohey, Shay, Yale University, New Haven, Connecticut, United States
  • Parikh, Chirag R., Yale University and VAMC, New Haven, Connecticut, United States
  • Patch, Daniel, IDEXX Laboratories, Westbrook, Maine, United States
  • Yerramilli, Maha, IDEXX Laboratories, Westbrook, Maine, United States
  • Farace, Giosi, IDEXX Laboratories, Westbrook, Maine, United States
  • Yerramilli, Murthy V., IDEXX Laboratories, Westbrook, Maine, United States
Background

Symmetric dimethylarginine (SDMA) is a byproduct of protein methylation and degradation that is primarily eliminated by the kidneys. It is freely filtered at the glomerulus, with no active secretion or reabsorption by the renal tubules. As a result, SDMA plasma concentrations are affected by changes in GFR and it is emerging as a kidney function biomarker that has outperformed serum creatinine in several studies. SDMA has traditionally been measured using liquid chromatography tandem mass spectrometry (LC-MS/MS), which is a major limitation for its widespread application as a screening marker for kidney function. The objective of this study is to validate a high throughput automated immunoassay for measuring SDMA in human serum.

Methods

Left-over serum samples were used for this study. SDMA was measured using novel immunoassay reagents manufactured by IDEXX Laboratories (Westbrook, ME) loaded on a Roche c501 analyzer (Indianapolis, IN). The assay was evaluated to establish its analytical measurement range (AMR), imprecision, specificity and accuracy. Method comparison with a separate LC-MS/MS was performed using serum collected from 50 adults with varied kidney function.

Results

The analytical measurement range of the SDMA immunoassay was 4.2 to 100.5 μg/ml. Total coefficient of variation (CV) was less than 13.1% at the three different concentrations tested. Hemolysis did not affect assay performance up to a hemolysis index of 186 and common drugs tested did not interfere. Deming regression analysis of the method comparison with the LC–MS/MS revealed a slope of 1.001, intercept of 1.4, and correlation coefficient of 0.99

Conclusion

A novel immunoassay for measuring SDMA with comparable performance to LC-MS/MS is now validated for use in humans and better suited for high-throughput clinical laboratory testing. This assay will facilitate further research and widespread clinical adoption of this emerging biomarker.

Comparison between IDEXX SDMA immunoassay on Roche c501 and an LC-MS/MS method

Funding

  • Commercial Support