# Comparison of Lipid Measurements by Clinical Chemistry and NMR Spectroscopy

## TL;DR

This study compares two methods for measuring lipids in blood samples and finds that one method works well for fresh samples but less so for frozen ones.

## Contribution

The study evaluates the reliability of NMR spectroscopy versus clinical chemistry for lipid profiling in fresh and frozen serum samples.

## Key findings

- Lipid measurements in fresh samples using clinical chemistry and NMR are strongly correlated (r ≥ 0.93).
- Freezing–thawing reduces correlation between NMR and clinical chemistry measurements, except for triglycerides.
- Lower concentration ranges of lipids show weaker correlations in both fresh and frozen samples.

## Abstract

Background/Objectives: Triglyceride (TG), Total Cholesterol (TC), HDL cholesterol (HDL-C), and LDL cholesterol (LDL-C) levels are commonly tested routine lipid profiles (RLPs) for assessing cardiovascular disease (CVD) risk. While lipid levels are typically measured by using standard clinical chemistry tests in routine practice, Nuclear Magnetic Resonance (NMR) spectroscopy has recently been explored for its ability to determine lipid levels under clinical settings. This study aims to compare RLP and NMR analysis using 17,337 fresh serum samples. Additionally, it investigates the impacts of freezing–thawing on these parameters in 9559 frozen samples. Methods: RLP was performed by employing the Siemens Dimension clinical chemistry system. Furthermore, the lipid contents of the fresh and frozen serum samples were evaluated across different concentration ranges. Results: Lipid parameters of fresh samples ascertained with RLP and NMR were strongly correlated (r ≥ 0.93). Analysis with frozen samples revealed that the correlation between lipid measurements decreased below r ≤ 0.86, except for TG (r = 0.97). Additionally, at different concentration ranges, the lower-level ranges for all lipid parameters in both fresh and frozen samples exhibited weaker correlations. Conclusions: This study demonstrates that NMR spectroscopy is a reliable, rapid, chemical-free method for lipid analysis in fresh samples. However, in frozen samples, relying on NMR to support RLP offers a less reliable approach for lipid measurement.