Abstract: TH-PO1122
Spurious Hyponatremia Due to Preanalytical Errors in Handling Frozen Serum Samples from a CKD of Unknown Etiology (CKDu) Research Centre
Session Information
- CKD: Therapies, Innovations, and Insights
November 06, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 2302 CKD (Non-Dialysis): Clinical, Outcomes, and Trials
Authors
- Kamboj, Kajal, Boston Medical Center, Boston, Massachusetts, United States
- Huynh, Courtney, Boston Medical Center, Boston, Massachusetts, United States
- Aceituno, Anna Marie, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Camilli, Samuel, Boston Medical Center, Boston, Massachusetts, United States
- Varanasi, Rama S, Boston University, Boston, Massachusetts, United States
- Brooks, Daniel R., Boston Medical Center, Boston, Massachusetts, United States
- Friedman, David, Harvard Medical School, Boston, Massachusetts, United States
- Bhalla, Vivek, Stanford University School of Medicine, Stanford, California, United States
- Waikar, Sushrut S., Boston Medical Center, Boston, Massachusetts, United States
Group or Team Name
- CKDu CURE Consortium.
Background
Several studies have shown that freezing serum samples can lead to concentration gradients of analytes if the thawed sample is not adequately mixed. In a pilot study of serum samples from a CKDu research site, we found implausible rates of severe hyponatremia (Na <100 meq/L) that led us to consider pre-analytical errors. We hypothesized that vortexing (as opposed to manual inversion) of thawed 4 mL serum samples led to inadequate mixing and concentration gradients as the cause.
Methods
To test this hypothesis, we collected and froze serum from 4 patients undergoing clinical laboratory testing for serum electrolytes in the Nephrology Clinic at Boston Medical Center. Serum was separated by centrifugation at 2000g for 12 min at 4°C. We then subjected serum samples to a variety of conditions to isolate the potential effects of freezing temperature, vortexing x10 seconds, or manual inversion x2 or x10 on measured analyte concentrations. Serum aliquots were collected from the top, middle, and bottom thirds of 4mL serum cryovials to test whether concentration gradients formed in vortexed vs. inverted samples. All study measurements were made in a CLIA certified laboratory and compared against clinical results from the same laboratory.
Results
Substantial concentration gradients from the top to bottom remain despite 10 seconds of vortexing of thawed samples; this was not observed with inverting the study tube x10 or even x2. Spurious hyponatremia (Na <110 meq/L) and hypernatremia (Na >160 meq/L) can be observed with vortexing depending on from where the aliquot is taken (Table).
Conclusion
Ten seconds of vortexing is insufficient to homogenize thawed serum, leading to artifactual sodium values due to stratification. Our results emphasize the critical importance of proper mixing of parent samples when subaliquots are made after thawing. The Consortium’s subaliquoting protocols have been revised accordingly.
Funding
- Other NIH Support