Quantification of HDL particle concentration by calibrated ion mobility analysis.
Level 4 - case-series / case-control
Analytical assay validation combined with a small case-control comparison
PubMed 25225166 · doi:10.1373/clinchem.2014.228114
What was done
Researchers developed and validated calibrated ion mobility analysis (calibrated IMA) to measure high-density lipoprotein particle concentration (HDL-P). HDL was isolated from plasma via ultracentrifugation, gas-phase ionized with electrospray ionization, separated by size, and counted as discrete particles. Purified proteins provided calibration curves to correct for ionization efficiency. The method was validated using gold nanoparticles and reconstituted HDL, and then tested in human plasma from 40 control participants and 40 participants with cerebrovascular disease.
What was found
Particle concentrations of gold nanoparticles and reconstituted HDLs measured by calibrated IMA matched orthogonal methods. In human plasma (n = 80), three HDL subspecies were reproducibly quantified, with a mean estimated total HDL-P of 13.4 (2.4) μmol/L. HDL-C accounted for 48% of the variance in HDL-P. HDL-P was significantly lower in participants with cerebrovascular disease than in controls (P = 0.002), remaining significant after adjustment for HDL cholesterol (P = 0.02). Apolipoprotein A-I stoichiometry was estimated at 3–4 molecules per HDL particle.
Why it matters
Existing HDL-P measurement methods yield concentrations differing by more than five-fold. Calibrated IMA provides a standardized, physical particle-counting method that enables accurate quantification of HDL particle subclasses independently of traditional cholesterol content measurements.
Limits
The clinical evaluation was cross-sectional and limited to a small sample size (n = 40 per group). The workflow requires manual isolation of HDL by ultracentrifugation prior to electrospray ionization, which limits immediate high-throughput clinical utility.
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