Ratio of remnant-like particle-cholesterol to serum total triglycerides isan effective alternative to ultracentrifugal and electrophoretic methods in the diagnosis of familial type III hyperlipoproteinemia

Background: Familial type III hyperlipoproteinemia (HLP) is characterized b y the presence of beta-migrating VLDL (beta-VLDL) and increased risk of car diovascular disease. Assessment of plasma beta-VLDL is achieved by measurin g the ratio of VLDL-cholesterol (VLDL-C) to total plasma triglycerides (TGs ) or by detecting beta-VLDL in total VLDL. The objective of this study was to compare the clinical utility of the ratio of remnant-like particle-chole sterol (RLP-C) to total TGs with that of the current methods for diagnosing type III HLP. Methods: Detection of beta-VLDL by electrophoresis of VLDL was used to defi ne type III HLP. Twenty-eight patients with type III HLP and 43 subjects la cking beta-VLDL were investigated. Fasting TG concentrations were >2.26 mmo l/L in all subjects. Subjects were separated into three groups: group 1, se rum total cholesterol less than or equal to 5.18 mmol/L (n = 11); group 2, total cholesterol >5.18 mmol/L and TGs between 2.26 and 9.04 mmol/L (n = 51 ); and group 3, TGs >9.04 mmol/L (n = 9). Results: In group 2, a RLP-C-to-total TG molar ratio greater than or equal to 0.23 (greater than or equal to 0.10 when using mg/dL) and a VLDL-C-to-to tal TG molar ratio greater than or equal to 0.69 (greater than or equal to 0.30 when using mg/dL) correctly classified 94% and 90% of the subjects, re spectively. The utility of the RLP-C-to-total TG ratio in diagnosing type I II HLP decreased in patients in the other two groups. Conclusion: When used in an appropriate target population, the RLP-C-to-tot al TG ratio is a convenient and effective alternative to ultracentrifugal a nd electrophoretic methods for diagnosing-type III HLP. (C) 1999 American A ssociation for Clinical Chemistry.