Context: The traditional lipid and lipoprotein levels in patients with familial combined hyperlipidemia (FCH) are relatively mildly elevated and do not fully explain the increased risk of CVD. In other populations, high remnant-like particle cholesterol (RLP-C) levels are an independent risk factor for CVD.

Objectives: To investigate whether plasma RLP-C concentrations are elevated in patients with FCH and contribute to the increased prevalence of CVD.

Design, Setting, Participants: In this cross-sectional study, we studied RLP-C levels in 37 FCH families comprising 582 subjects, of whom 134 subjects were diagnosed FCH based on total cholesterol, triglyceride and apoB levels. Plasma RLP-C concentrations were determined using an immuneseparation technique.

Results: For both men and women, the mean plasma RLP-C concentration (mmol/l) was two-fold elevated in FCH patients (0.59 (0.54-0.66) and 0.40 (0.37-0.43), respectively) compared to both normolipidemic relatives (0.27 (0.26-0.29) in male and 0.22 (0.21-0.23) in female, all p < 0.000) and spouses (0.27 (0.23-0.31) in male and 0.24 (0.21-0.27) in female), all P<0.000). Plasma RLP-C levels above the 90th percentile predicted prevalent CVD, independently of nonlipid cardiovascular risk factors (OR 2.18 [1.02-4.66]) and independently of triglyceride levels (OR 2.35 [1.15-4.83]). However, in both FCH patients and controls, RLP-C did not provide additional information about prevalent CVD over and above non-HDL cholesterol levels.

Conclusion: Patients with FCH have two-fold elevated plasma RLP-C levels, which add to the atherogenic lipid profile and contribute to the increased risk for CVD. However, for clinical practise, non-HDL cholesterol is the best predictor of prevalent CVD.