Hyperlipoproteinemia laboratory findings
Lipoprotein Disorders Microchapters
Complete fasting lipid profile should be obtained for making the diagnosis of hyperlipidemia and risk stratification for coronary heart diseases. In the absence of symptoms or signs suggestive of a particular disorder, a limited workup should also be performed to rule out secondary hyperlipidemias.
Complete Lipid Profile
The US National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) suggests screening asymptomatic individuals with a complete fasting lipid profile every 5 years, with a shorter interval for those with high-normal lipid levels and longer interval for low-risk individuals with low or normal lipid levels. Obtain complete lipid profile after 9 to 12-hour fast. The reference values according to ATP III classification for making the diagnosis and risk stratification are depicted below:
|Levels of Total Cholesterol (mg/dL)|
|200 - 239||Borderline high|
|Levels of LDL Cholesterol (mg/dL)|
|100 - 129||Near optimal|
|130 - 159||Borderline high|
|160 - 189||High|
|≥ 190||Very high|
|Levels of HDL Cholesterol (mg/dL)|
|Levels of Serum Triglycerides (mg/dL)|
|150 - 199||Borderline high|
|200 - 499||High|
|≥ 500||Very high|
|Levels of VLDL Cholesterol (mg/dL)|
Other Laboratory Tests
For careful medical evaluation, physicians must take into consideration all medications (both prescription and over-the-counter medications) and perform following tests to rule out secondary hyperlipidemias:
- Random blood sugar
- Serum thyroid-stimulating hormone
- Liver function tests
- Renal function tests
Other tests that may be done to have a definitive diagnosis include:
- Apobetalipoprotein (apoB) quantification (by ultracentrifugation and electrophoresis)
- Studies of cells called fibroblasts (to see how the body absorbs LDL cholesterol)
- Gene analysis or receptor analysis (to identify the specific defect associated with hyperlipidemia)
Many different types of mutations have been identified in the LDL-receptor (LDLR) gene. They have been categorized into four classes of alleles based on the phenotypic behavior of the mutant protein:
- Class I - Null, in which LDL-receptor synthesis is defective.
- Class II - Transport defect, in which intracellular transport from the endoplasmic reticulum to the Golgi apparatus is defective.
- Class III - Binding defect, in which LDL-receptors are synthesized and transported to the cell surface normally, but binding of LDL-cholesterol is defective.
- Class IV - Internalization defect, in which the LDL-receptors reach the cell surface and bind LDL-cholesterol normally, but LDL internalization is defective.
Shown below is a diagnostic algorithm to diagnose hyperlipidemia.
|Triglycerides > 75th Percentile||NO||Type IIa|
|Types I, IIb, IV, V|
|Total Cholesterol/Apo B ratio ≥ 6.2||NO||Types IIb, IV|
|Types I, III, V|
|Triglycerides/Apo B ratio < 10.0||NO||Types I, V|
- National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) (2002). "Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report.". Circulation. 106 (25): 3143–421. PMID 12485966.
- Guardamagna O, Restagno G, Rolfo E, Pederiva C, Martini S, Abello F; et al. (2009). "The type of LDLR gene mutation predicts cardiovascular risk in children with familial hypercholesterolemia.". J Pediatr. 155 (2): 199–204.e2. PMID 19446849. doi:10.1016/j.jpeds.2009.02.022.
- Hobbs HH, Russell DW, Brown MS, Goldstein JL (1990). "The LDL receptor locus in familial hypercholesterolemia: mutational analysis of a membrane protein.". Annu Rev Genet. 24: 133–70. PMID 2088165. doi:10.1146/annurev.ge.24.120190.001025.
- Sniderman A, Tremblay A, Bergeron J, Gagné C, Couture P (2007). "Diagnosis of type III hyperlipoproteinemia from plasma total cholesterol, triglyceride, and apolipoprotein B". Journal of Clinical Lipidology. 1 (4): 256–63. PMID 21291689. doi:10.1016/j.jacl.2007.07.006. Retrieved 2012-10-24.