Phospholipids, Serum

CPT CODE:

USEFUL FOR:

First-order test in the diagnosis of LCAT deficiency

SPECIMEN REQUIRED:

Draw blood in a plain, red-top tube(s) or a serum gel tube(s) following an overnight (12-14 hour) fast. Patient must not consume any alcohol for 24 hours before the specimen is drawn. Spin down and send 1 mLof serum frozen in plastic vial.

TRANSPORT TEMPERATURE:

Frozen\Refrig <7 days OK\Ambient NO

CLINICAL INFORMATION:

The phospholipids comprise about 1/3 of the total lipids in serum.These consist in a large part of a lipid, phosphatidylcholine (formerlylecithin), in which 1 of the glycerol carbons is esterified with cholinephosphate. A major step in lipoprotein particle remodeling results fromlecithin-cholesterol acyltransferase (LCAT) activity, which normallytransesterifies free cholesterol with fatty acids derived fromphosphatidylcholine. LCAT deficiency results in a lack of remodelingof primary lipoprotein particles, affecting eventual cholesterol uptakeand elimination. In cases of deficiency of LCAT, the concentration oflecithin in the serum are increased several-fold.
Clinical findings in LCAT deficiency include corneal opacities, anemia, and frequently, proteinuria. The disorder is inherited as an autosomal recessive trait. Early atherosclerosis develops in many individuals with this disorder.
In addition, sphingomyelin normally comprises about 5% to 20% ofthe total phospholipids of serum. In Niemann-Pick Type A and Bdiseases, sphingomyelin accumulates in visceral and neural tissuesand may become increased in the serum.
Other disorders involving alterations of the concentration, composition, and/or lipoprotein distribution include:  abeta- or hypobetalipoproteinemia,Tangier disease, or fish eye disease.

CLINICAL INTERPRETATION:

Elevated in cases of LCAT deficiency due to elevations of lecithin

REFERENCE VALUES:

155-275 mg/dL