Hyperlipoproteinemia laboratory findings

Lipoprotein Disorders Microchapters
Patient Information
Overview
Causes
Classification Hyperlipoproteinemia Hypolipoproteinemia
Treatment

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]

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.Guardamagna O, Restagno G, Rolfo E, Pederiva C, Martini S, Abello F, Baracco V, Pisciotta L, Pino E, Calandra S, Bertolini S (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. CS1 maint: Multiple names: authors list (link) 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.

Approach

Shown below is a diagnostic algorithm to diagnose hyperlipidemia.

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