The Apo E Genotype Test for
Type III Hyperlipoproteinemia
Type III hyperlipoproteinemia (broad beta disease) should be considered in all patients with elevation of both serum cholesterol and triglycerides. The DNA test for this lipid disorder accurately determines the apolipoprotein E (apo E) genotype. The apo E genotype E2/E2 is diagnostic of type III hyperlipoproteinemia in individuals who have elevated serum cholesterol and triglycerides and accumulation of the abnormal lipoprotein ß-VLDL. Apo E genotyping is also of value for risk determination in relatives. Type III hyperlipoproteinemia is associated with accelerated atherosclerosis, coronary heart disease and peripheral vascular disease.
Indications for Apo E Genotype Testing:
Total serum cholesterol >240 mg/dl and triglycerides (TG) >150 mg/dl
OR
LDL cholesterol >[age + 100] and TG >[age + 100]
PLUS
VLDL cholesterol/TG ratio >0.3
OR
ß-VLDL revealed by lipoprotein electrophoresis as a "broad beta band"
Patients may present with:
•
No symptoms
•
Peripheral vascular disease
•
Coronary artery disease (coronary heart disease)
•
Cutaneous xanthomas
•
Diabetes mellitus, obesity or hypothyroidism (conditions which can trigger type III hyperlipoproteinemia in individuals with the apo E genotype E2/E2)
Relatives of individuals diagnosed with type III hyperlipoproteinemia, especially siblings
Recommended sequence of tests for patients with elevated cholesterol and triglycerides:
1.
Lipoprotein analysis (lipid panel) after a 12 hour fast to determine levels of total serum cholesterol, TG, HDL cholesterol and estimated LDL cholesterol.
2.
VLDL cholesterol quantitation to calculate the VLDL cholesterol /TG ratio. A ratio of >0.3 is highly suggestive of broad beta disease. This test also includes lipoprotein electrophoresis to identify ß-VLDL (broad beta band).
3.
Apo E genotype test to identify the apo E2/E2 genotype. This genotype is diagnostic for type III
hyperlipoproteinemia when associated with elevation of serum cholesterol and TG.
Apo E Genotype Testing Services:
Diagnostic testing for type III hyperlipoproteinemia
Predisposition testing in relatives
Detailed reports with genetic interpretation, recommendations, and education
Genetic consultation by board certified genetic counselors and geneticists
Referral to a collaborating lipid laboratory for special lipid testing (VLDL quantitation and lipoprotein electrophoresis)
Clinical consultations regarding type III hyperlipoproteinemia and other dyslipidemias may be arranged
Method: Apo E genotype testing involves DNA analysis by polymerase chain reaction (PCR) with restriction enzyme cleavage.
Accuracy: >99%
Specimen requirements: 5 ml whole blood in an EDTA tube (lavender top). Store and ship at room temperature.
Turnaround time: 1 day
Please call Kimball Genetics for more information.
•