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Test ID: LCATD    
Lecithin Cholesterol Acyltransferase Deficiency Profile

Useful For Suggests clinical disorders or settings where the test may be helpful

Detection of lecithin cholesterol acyltransferase deficiency

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Lecithin cholesterol acyltransferase (LCAT), a glycoprotein with an apparent molecular weight of 67 kD, is the enzyme responsible for synthesizing the majority of cholesteryl esters in serum. It acts by transferring fatty acid from phosphatidylcholine to the 3-hydroxyl group of cholesterol. In serum, LCAT protein is bound to high-density lipoproteins (HDL) and it esterifies cholesterol primarily in this class of lipoproteins. The major structural protein of HDL, apolipoprotein AI (apo AI), is believed to be the principal activator of LCAT. There is evidence that serum LCAT also may act directly on lower-density lipoproteins.

 

It is believed that LCAT regulates the transport of cholesterol between extravascular pools. In the theoretical pathway, known as reverse cholesterol transport, cholesterol is moved from peripheral tissues to the liver for catabolism. The esterification of cholesterol by LCAT in serum serves to maintain a chemical concentration gradient for unesterified cholesterol between peripheral cells and the serum.

 

Plasma lysophosphatidylcholine (LPC) is 1 of the products of LCAT and as such, LPC concentration is diminished in patients with LCAT deficiency.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

CHOLESTEROL, TOTAL

The National Cholesterol Education Program (NCEP) has set the following guidelines (reference values):

Desirable: <200 mg/dL

Borderline high: 200-239 mg/dL

High: > or =240 mg/dL

Also see age and sex adjusted reference values in Total Cholesterol-Percentile Ranking in Lipids and Lipoproteins in Blood Plasma (Serum) in Special Instructions.

 

CHOLESTERYL ESTERS

60-80% of total cholesterol

Reference values have not been established for patients that are <16 years of age.

 

PHOSPHOLIPIDS

155-275 mg/dL

Reference values have not been established for patients that are <16 years of age.

 

LYSOPHOSPHATIDYLCHOLINE

16:0 Lysophosphatidylcholine: > or =62 mcmol/L

18:0 Lysophosphatidylcholine: > or =20 mcmol/L

Reference values have not been established for patients that are <16 years of age.

 

INTERPRETATION

No evidence of decreased lecithin cholesterol acyltransferase activity

Definitive results and an interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

Norum-Gjone disease is a severe form of lecithin cholesterol acyltransferase (LCAT) deficiency characterized by:

-Diminished serum levels of cholesterol ester (<50%)

-Increased serum levels of nonesterified cholesterol

-Increased serum levels of phospholipids

-Decreased concentration of lysophosphatidylcholine

-Decreased high-density lipoproteins (HDL)

-Increased triglycerides

 

Fish-eye disease, a less severe form of LCAT deficiency, generally demonstrates less severe changes in the parameters that are measured. Fish-eye disease appears to be specifically associated with esterification of HDL cholesterol.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

If lecithin cholesterol acyltransferase (LCAT) deficiency is suspected from initial tests, analysis of triglycerides and high-density lipoproteins (HDL) cholesterol will be performed at no charge. If fish-eye disease is suspected, percent cholesterol ester in the HDL fraction will be measured.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Norum KR, Gjone E: Familial serum-cholesterol esterification failure. A new inborn error of metabolism. Biochim Biophys Acta 1967;144:698-700

2. Carlson LA, Philipson B: Fish-eye disease. A new familial condition with massive corneal opacities and dyslipoproteinaemia. Lancet II 1979;2:922-924

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test