Greg Sommer, Laura Fredriksen, Gabriela Iacovetti, Kyungjin Hong, and Ulrich Schaff, Sandstone Diagnostics, Inc.

Journal of Clinical Oncology 2019 37:15_supple14529-e14529

 

ABSTRACT

Background

Sample quality is a critical consideration for high fidelity cell-free DNA (cfDNA) testing. Oncological cfDNA tests used for liquid biopsy typically employ specialty blood collection tubes containing chemical preservatives to minimize degradation of samples prior to lab testing. Here we describe a newly developed device, Zero Delay Plasma– a portable centrifuge and disc system designed to immediately isolate cell-free plasma at the point of blood draw – and evaluate its performance against the Streck cfDNA collection tube.

Methods

Whole blood was collected, processed, and stored at room temperature for up to 7 days with both the Zero Delay Plasma system and the Streck cfDNA blood collection tube. Sample hemolysis was measured via cell-free hemoglobin. Genomic contamination and cfDNA signal-to-noise were evaluated by qPCR and electrophoresis, comparing signal from target 150-200bp cfDNA to contaminating longer length genomic sequences in the sample. 2 sets of hemolysis experiments, 2 sets of electrophoresis experiments and 4 sets of qPCR experiments were conducted.

Results

Plasma processed with the Zero Delay Plasma system yielded ~4X lower hemolysis levels, ~10X lower genomic contamination, and ~20X higher cfDNA signal-to-noise compared to the Streck cfDNA collection tube after 7 days of storage at room temperature.

Conclusions

The Zero Delay Plasma system minimizes sample degradation and analytical background signal for cfDNA testing by immediately removing cells and other contaminants at the point of blood collection. Clinical evaluations are in process.

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