Characteristic comparison of triglyceride-rich remnant lipoprotein measurement between a new homogenous assay (RemL-C) and a conventional immunoseparation method (RLP-C)

BACKGROUND: Increased serum remnant lipoproteins are supposed to predict cardiovascular disease in addition to increased LDL. A new homogenous assay for remnant lipoprotein-cholesterol (RemL-C) has been developed as an alternative to remnant-like particle-cholesterol (RLP-C), an immunoseparation assay, widely used for the measurement of remnant lipoprotein cholesterol. METHODS: We evaluated the correlations and data validation between the 2 assays in 83 subjects (49 men and 34 women) without diabetes, hypertension and medications for hyperlipidemia, diabetes, and hypertension, and investigated the characteristics of remnant lipoproteins obtained by the two methods (RLP-C and RemL-C) and their relationships with IDL-cholesterol determined by our developed HPLC method. RESULTS: A positive correlation was significantly found between the two methods (r = 0.853, 95%CI 0.781–0.903, p < 0.0001). Bland & Altman analysis revealed that RemL-C values were likely to be significantly higher than RLP-C values, particularly in samples with high levels of remnant lipoproteins. Several data dissociations between the RemL-C and RLP-C were also observed. The HPLC chromatograms show high concentrations of chylomicron cholesterol in serum samples with RemL-C level < RLP-C level, but high concentrations of IDL-cholesterol in samples with RemL-C level > RLP-C level. RemL-C (r = 0.339, 95%CI 0.152–0.903; p = 0.0005) significantly correlated with IDL-cholesterol, but not RLP-C (r = 0.17, 95%CI -0.047–0.372; p = 0.1237) in all the samples (n = 83). CONCLUSION: These results suggest that there is generally a significant correlation between RemL-C and RLP-C. However, RemL-C assay is likely to reflect IDL more closely than RLP-C.