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]

Overview

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.

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
Levels of VLDL Cholesterol (mg/dL)
< 30	Normal
≥ 30	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:

• 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.

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