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Low Density Lipid Apheresis

Description

Low-density lipoprotein apheresis describes a variety of technologies used to acutely remove low density lipoprotein (LDL) from the plasma. The patient initially undergoes an apheresis procedure to isolate the plasma. The low density lipoproteins are then selectively removed from the plasma by immunoadsorption, heparin-induced extracorporeal LDL precipitation (also referred to as HELP) or dextra sulfate adsorption. In immunoadsorption, polyclonal antihuman apoB antibodies from sheep selectively bind and remove LDL. (ApoB is the protein moiety of low density lipoprotein.) In HELP, LDL and other particles containing apoB are precipitated by heparin at an acidic pH. Dextran sulfate adsorption removes LDL by binding the positively charged apoB to dextran sulfate particles bound to cellulose. LDL apheresis must be distinguished from plasma exchange (also referred to as plasmapheresis). In plasma exchange the plasma is collected during a pheresis procedure then discarded and replaced with crystalloids. In contrast, LDL apheresis is a selective procedure in which only pathogenic low density lipoproteins are removed. The plasma is then returned to the patient. Plasma exchange is addressed in a separate policy Therapeutic Apheresis, Medicine, Policy No. 5.

LDL apheresis has been investigated as a technique to treat patients with familial hypercholesterolemia (FH). FH is a dominantly inherited disorder involving a mutation of the gene that encodes for the specific cell surface receptor responsible for LDL receptors is halved in this condition, resulting in serum LDL-C levels that are approximately two to three times acceptable levels (i.e., >300 mg/dL). Affected male patients typically develop coronary heart disease in their thirties and forties, while women develop coronary heart disease in their fifties. Heterozygous FH may or may not respond adequately to lipid-lowering drugs.

Homozygous hypercholesterolemia is rare, occurring in only 1 in 1 million subjects. Serum levels of LDL-C may be elevated six fold (>500 mg/dL), due to the total lack of functioning LDL receptors. Homozygotes develop severe aortic stenosis and coronary heart disease by age 20. These patients typically do not respond adequately to drug or diet modification therapy. In the past, patients with homozygous FH may have been treated with plasma exchange, but the advent of LDL apheresis provides a more targeted approach by permitting selective removal of LDL from the plasma.

Two lipid apheresis systems have received FDA approval. The Liposorber LA 15® System dextran sulfate system was granted FDA approval in 1996. The heparin-induced extracorporeal LDL precipitation (HELP®) system received FDA approval in 1997.

Policy/Criteria

LDL apheresis may be considered medically necessary in patients with homozygous familial hypercholesterolemia as an alternative to plasmapheresis.

LDL apheresis may be considered medically necessary in patients with heterozygous familial hypercholesterolemia who have failed a 6-month trial of diet therapy and maximum tolerated combination drug* therapy AND who meet the following FDA-approved indications: (All LDL levels represent the best achievable LDL level after a program of diet and drug therapy.):

  1. Functional hypercholesterolemic heterozygotes with LDL greater than or equal to 300 mg/dL
  2. Functional hypercholesterolemic heterozygotes with LDL greater than or equal to 200 mg/dL AND documented coronary artery disease*
*For definitions of maximum tolerated drug therapy and documented coronary artery disease, please see policy guidelines below.

Policy Guidelines

Maximum tolerated drug therapy is defined as a trial of drugs from at least two separate classes of hypolipidemic agents such as bile acid sequestrants, HMG-CoA reductase inhibitors, fibric acid derivatives, or Niacin/Nicotinic acids.

Documented coronary artery disease includes a history of myocardial infarction, coronary artery bypass surgery, percutaneous transluminal coronary angioplasty or alternative revascularization procedure, or progressive angina documented by exercise or non-exercise stress test.

Frequency of LDL apheresis varies, but typically averages about once every two weeks to obtain an interapheresis level of LDL cholesterol at least than 120 mg/dl. Patients with homozygous FH may be treated more frequently. Patients are simultaneously treated with diet and drug therapy.

CPT code 36520 (therapeutic apheresis is used to code for the apheresis procedure). There is no specific CPT or HCPCS code for the disposable supplies associated with LDL apheresis. For example, dextran sulfate systems (e.g., Liposorber LA-15 System) require the use of a disposable column consisting of dextran sulfate ligands on cellulose beads.

Rationale for Benefit Administration

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Scientific Background

This policy is based primarily on a 1999 TEC assessment (1) that offered the following observations and conclusions:

  1. Three randomized controlled trials report that lipid apheresis is associated with clinically and statistically significantly greater reduction in LDL cholesterol than that achieved by medication alone for patients with refractory hypercholesterolemia.
  2. Nonrandomized studies included patients who had failed diet and medication therapy. The efficacy of LDL lowering was of similar magnitude compared to that observed in the randomized studies.
  3. There is currently insufficient direct evidence to demonstrate that the reductions in LDL cholesterol seen with LDL apheresis will result in reduced adverse cardiovascular events. However, given the established causal relationship of LDL cholesterol and cardiac events, such an effect is likely, particularly given the fact that LDL apheresis acutely lowers the LDL cholesterol by 50% to 70% or more.

An updated 2001 search of the literature reveals additional published clinical study results and reviews which further support the current clinical indications for LDL apheresis.(2)

References

  1. 1999 TEC Assessment; Tab 3
  2. Schmaldienst S, Banyai S, Stulnig G, et al. Prospective randomized crossover comparison of three LDL-apheresis systems in statin pretreated patients with familial hypercholesterolemia. Atherosclerosis 2000; 151: 493-499.

Cross References

Therapeutic Apheresis, Medicine, Policy No. 5

CodesNumberDescription
CPT36520Therapeutic apheresis
BCBSAS2120Low density lipoprotein (LDL) apheresis using
heparin-induced extracorporeal LDL precipitation



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