Diagnosis of type III hyperlipoproteinemia from plasma total cholesterol, triglyceride, and apolipoprotein B.

Objective: Our objective was to develop a simple algorithm that could be applied in routine clinical practice to diagnose type III hyperlipoproteinemia based on plasma total cholesterol, triglyceride and apolipoprotein (Apo) B. Methods: Analysis of plasma lipid, lipoprotein lipid, and apolipoprotein data from 1771 patients in a tertiary care lipid clinic, from whom all data had been collected prospectively by standardized methods. Of the 1771, based on the Fredrickson classification, 16 had type I hyperlipoproteinemia, 736 type IIa hyperlipoproteinemia, 371 type IIb hyperlipoproteinemia, 38 type III hyperlipoproteinemia, 509 type IV hyperlipoproteinemia, and 101 type V hyperlipoproteinemia. Results: Mean plasma ApoB was highest in type IIb (1.53 ± 0.36 g/L), borderline high (1.1 ± 0.23 g/L) in type IV, normal in type III and type V (1.04 ± 0.21 g/L and 0.96 ± 0.40 g/L, respectively) and low in type I (0.48 ± 0.16 g/L). In type III hyperlipoproteinemia, very low–density lipoprotein ApoB (ie, d<1.006 g/mL) accounted for 42.3% of total ApoB, a value that was substantially higher than in any of the other dyslipoproteinemias. The total cholesterol (TC)/ApoB ratio was similar in the uncommon dyslipoproteinemias—type I, III, and V hyperlipoproteinemia (10.5 ± 4.8, 8.7 ± 1.8, 10.3 ± 7.7, respectively)—and much higher than in the common dyslipoproteinemias—type IIa, IIb, and type IV hyperlipoproteinemia (5.0 ± 0.4, 4.6 ± 0.4, 4.9 ± 1.1, respectively). Notwithstanding that the TC/ApoB area under the curve-receiver operating characteristic (AUC-ROC) was very high (0.93), it did not discriminate among the uncommon dyslipoproteinemias. However, the triglyceride (TG)/ApoB ratio was much higher in type I (42.4 ± 28.8) and type V (25.6 ± 30.2) than in type III (5.8 ± 3.2). All cases of type III had a TC/ApoB ratio >6.2 and a TG/ApoB ratio of <10.0. Using these cutpoints, there were also no false positives. Based on the TC/ApoB ratio and the TG/ApoB ratio, the AUC-ROC was 0.99. Conclusions: These data indicate that type III hyperlipoproteinemia can be reliably diagnosed based on plasma cholesterol, TG, and ApoB. [Copyright &y& Elsevier]