Hyperlipoproteinemia laboratory findings: Difference between revisions
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*Studies of cells called fibroblasts (to see how the body absorbs LDL cholesterol) | *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) | *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.{{cite journal |author=Guardamagna O, Restagno G, Rolfo E, Pederiva C, Martini S, Abello F | Many different types of mutations have been identified in the LDL-receptor (LDLR) gene.<ref name="pmid19446849">{{cite journal| author=Guardamagna O, Restagno G, Rolfo E, Pederiva C, Martini S, Abello F et al.| title=The type of LDLR gene mutation predicts cardiovascular risk in children with familial hypercholesterolemia. | journal=J Pediatr | year= 2009 | volume= 155 | issue= 2 | pages= 199-204.e2 | pmid=19446849 | doi=10.1016/j.jpeds.2009.02.022 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19446849 }} </ref> They have been categorized into four classes of alleles based on the phenotypic behavior of the mutant protein:<ref name="pmid2088165">{{cite journal| author=Hobbs HH, Russell DW, Brown MS, Goldstein JL| title=The LDL receptor locus in familial hypercholesterolemia: mutational analysis of a membrane protein. | journal=Annu Rev Genet | year= 1990 | volume= 24 | issue= | pages= 133-70 | pmid=2088165 | doi=10.1146/annurev.ge.24.120190.001025 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=2088165 }} </ref> | ||
*Class I - Null, in which LDL-receptor synthesis is defective. | *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 II - Transport defect, in which intracellular transport from the endoplasmic reticulum to the Golgi apparatus is defective. | ||
Revision as of 19:31, 24 October 2012
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Lipoprotein Disorders Microchapters |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hardik Patel, M.D., Aditya Govindavarjhulla, M.B.B.S. [2]
Overview
Laboratory Findings
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 | Desirable |
| 200 - 239 | Borderline high |
| ≥ 240 | High |
| Levels of LDL cholesterol (mg/dl) | |
| < 100 | Optimal |
| 100 - 129 | Near optimal |
| 130 - 159 | Borderline high |
| 160 - 189 | High |
| ≥ 190 | Very high |
| Levels of HDL Cholesterol (mg/dl) | |
| < 40 | Low |
| ≥ 60 | High |
| Levels of serum triglycerides (mg/dl) | |
| < 150 | Normal |
| 150 - 199 | Borderline high |
| 200 - 499 | High |
| ≥ 500 | Very high |
Other Laboratory Tests
For careful medical evaluation, 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
- HbA1c
- Serum thyroid-stimulating hormone
- Liver function tests
- Renal function tests
- Urinalysis
Other tests that may be done to have a definitive diagnosis include:
- 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.[1] They have been categorized into four classes of alleles based on the phenotypic behavior of the mutant protein:[2]
- 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.
Approach
Shown below is a diagnostic algorithm to diagnose hyperlipidemia.[3]
| Hyperlipidemia | |||||||||||||||||||||||||||||||||||||||||
| Triglycerides > 75th Percentile | NO | Type IIa | |||||||||||||||||||||||||||||||||||||||
| YES | |||||||||||||||||||||||||||||||||||||||||
| Types I, IIb, IV, V | |||||||||||||||||||||||||||||||||||||||||
| Total Cholesterol/Apo B ratio ≥ 6.2 | NO | Types IIb, IV | |||||||||||||||||||||||||||||||||||||||
| YES | |||||||||||||||||||||||||||||||||||||||||
| Types I, III, V | |||||||||||||||||||||||||||||||||||||||||
| Triglycerides/Apo B ratio < 10.0 | NO | Types I, V | |||||||||||||||||||||||||||||||||||||||
| YES | |||||||||||||||||||||||||||||||||||||||||
| Type III | |||||||||||||||||||||||||||||||||||||||||
References
- ↑ 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. doi:10.1016/j.jpeds.2009.02.022. PMID 19446849.
- ↑ 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. doi:10.1146/annurev.ge.24.120190.001025. PMID 2088165.
- ↑ 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. doi:10.1016/j.jacl.2007.07.006. PMID 21291689. Retrieved 2012-10-24. Unknown parameter
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