Blood cleansing gets report card.

Blood cleansing gets report card

Plasmapheresis is one of those medical procedures that seem to make inherent sense: Where a blood-borne agent such as an antibody is responsible for a disease, treat the illness by essentially washing the culprit out of the blood Clinical experience doesn't always go along with what seems to make sense, though. Last week, a panel of experts concluded that plasmapheresis is useful in treating certain neurological diseases in which antibodies are suspected of causing the problem, but not in others.

After reviewing sometimes-conflicting data from clinical trials, the panel, which was convened by the National Institutes of Health in Bethesda, Md., declared that plasmapheresis is helpful in treating Guillain-Barre syndrome and acute myasthenia gravis but is not useful in amyotrophic lateral sclerosis (ALS). According to the panel, more data are needed to determine its value in multiple sclerosis and other neurological diseases.

In the procedure, which costs about $1,000, blood is removed from the patient and centrifuged to separate the plasma from the blood cells. The cells are put back into the patient, along with a reconstituted plasma component from donated blood. Each year about 15,000 people with neurological diseases in the United States undergo plasmapheresis; another 15,000 undergo it for other conditions such as metabolic disorders.

In myasthenia gravis, a condition marked by muscle weakness and fatigue, plasmapheresis removes an antibody against a receptor on muscle cells that normally responds to a nerve signal. While researchers have yet to conduct a trial comparing plasmapheresis to sham treatment, uncontrolled trials suggest it helps during acute stages of the disease when respiratory function is seriously impaired, the panel found.

The panel also concluded that plasmapheresis is useful in managing Guillain-Barre syndrome, characterized by loss of muscle strength, reflexes and sensation. As with myasthenia gravis, no controlled trials have been done, but the panel recommends the procedure for patients with severe weakness. Since the cause of the syndrome is unknown, the efficacy of plasmapheresis "challenges us to figure out what it is in the patient that is being removed," says Barry G. Arnason of the University of Chicago, who headed the panel.

But plasmapheresis isn't of help in ALS, a disease marked by unrelenting deterioration of the nerves that stimulate voluntary muscles. "The fact that [plasmapheresis] isn't helpful makes the possibility that ALS is an autoimmune disease less likely," says Arnason.