Lipoprotein phenotyping is an extension of the information obtained through lipoprotein fractionation and provides another approach to correlating laboratory findings with disease.

Six different lipoprotein distribution patterns (phenotypes) are seen in serums with high levels of cholesterol or triglycerides or both. These phenotypes, which are referred to by their assigned numbers, have been correlated with genetically determined abnormalities (familial or primary hyperlipoproteinemias) and with a variety of acquired conditions (secondary hyperlipoproteinemias).

Phenotype descriptions have proved useful in classifying diagnoses and in evaluating treatment and preventive regimens. Most hyperlipemic serums can be categorized into lipoprotein phenotypes without performing electrophoresis if the following are known: (1) chylomicron status, (2) serum triglyceride level, (3) total cholesterol, and (4) HDL cholesterol.

Table 5-15 shows the clinical significance of each of the lipoprotein phenotypes as primary familial syndromes and as secondary occurrences caused by disorders that alter lipid metabolism.

	Phenotype
	I	IIa	IIb	III	IV	V
Frequency	Very rare	Common	Common	Uncommon	Very common	Rare
Chylomicrons		Normal	Normal	Normal or	Normal
Pre--lipoproteins (approximates VLDL)				(these two  bands merge)
-Lipoproteins (approximates LDL)					Normal or	Normal or
1-Lipoproteins (approximates HDL)		Normal	Normal	Normal	Normal or	Normal or
Total cholesterol	Normal or				Normal or
Total triglycerides		Normal		or	or
Refrigerated serum or plasma	"Cream"/clear or turbid	Clear	+ or ++ turbid	+++ turbid	+++ turbid	"Cream"/  ++turbid

From Sacher, RA, and McPherson, RA: Widmann's Clinical Interpretation of Laboratory Tests, ed 11. FA Davis, Philadelphia, 2000, p 476, with permission.

• Failure to follow usual diet for 2 weeks before the test may yield results that do not accurately reflect client status.
• Ingestion of alcohol 24 hours before and food 12 hours before the test may alter results.
• Excessive exercise 12 hours before the test may alter results.
• Numerous drugs, including those that are known to alter lipoprotein components (see Tables 5-12, 5-13, and 5-15) may alter results.

• Further evaluation of elevated serum cholesterol levels and results of lipoprotein and cholesterol fractionation
• Family history of primary hyperlipoproteinemia (hyperlipidemia)
• Identification of the client's specific lipoprotein phenotype
• Known or suspected disorders associated with the several lipoprotein phenotypes (see Table 5-15)

Nursing Care Before the Procedure

General client preparation is the same as that for any study involving collection of a peripheral blood sample (see Appendix I).

• For this test, the client should ingest a normal diet, so that no weight gain or loss will occur for 2 weeks before the study, and should abstain from alcohol for 24 hours and from food for 12 hours before the test.
• Water is not restricted.
• The client also should avoid excessive exercise for at least 12 hours before the test.
• It also is recommended that drugs that may alter lipoprotein components be withheld for 24 to 48 hours or longer before the test (see Tables 5-12, 5-13, and 5-15), although this practice should be confirmed with the person ordering the study.

A venipuncture is performed and the sample collected in either a red- or lavender-topped tube, depending on the laboratory's procedure for determining lipoprotein phenotypes. The sample should be sent to the laboratory immediately.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Resume food and any drugs withheld before the test, as well as usual activities.