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

ObjectiveOur 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.MethodsAnalysis 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.ResultsMean 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.ConclusionsThese data indicate that type III hyperlipoproteinemia can be reliably diagnosed based on plasma cholesterol, TG, and ApoB.