Quantitative determination of serum LDL cholesterol by near-infrared spectroscopy

The aim of this study was to assess the feasibility of near infrared (near-IR) spectroscopy for the simultaneous quantitation of the four serum analytes making up the cardiac risk profile, including total cholesterol, triglycerides, HDL cholesterol, and LDL cholesterol. A total of 187 serum samples were obtained randomly from the central clinical chemistry laboratory of a large hospital, and the near-IR spectrum (400-2500 nm) recorded for each. Triglycerides and total cholesterol were determined using a Hitachi 717 analyzer, with enzymatic, colorimetric detection schemes, and HDL determined via a homogeneous assay on the same analyzer. The LDL cholesterol concentrations were then evaluated for each specimen using the Friedewald formula. Partial least squares (PLS) regression analysis was then used to quantitatively correlate the IR spectra with the reference assays. The near-IR method provides LDL cholesterol levels with RMS difference of 0.43 mmol/L as compared to the Friedewald approximate values, and total cholesterol and triglyceride levels consistent with previous near-IR studies. No satisfactory calibration could be derived for HDL cholesterol.