For many years the only clinical use of plasmapheresis was to alleviate the hyperviscosity syndrome of Waldenstrom's macroglobulinemia. In 1976 three articles in the Lancet detailed its use in Goodpasture's syndrome, systemic lupus erythematosus and myasthenia gravis. Since then reports of its use in over 180 different conditions have appeared. In most of these diseases plasmapheresis has been shown to be ineffective or to offer no clear benefit over conventional treatment. In 1981 a report that plasmapher esis was an effective treatment of rheumatoid arthritis was threatening to add $28 billion to the American health care budget. Controlled clinical trials have delineated only very few clinical conditions in which plasmapheresis is an effective component of treatment. These include Goodpasture's syndrome, the Guillain-Barre syndrome, Waldenstrom's macroglobulinemia, myasthenic crisis, cryoglobulinemia, thrombotic thrombocytopenic purpura, polyarteritis nodosa associated with hepatitis B virus, homozygous hypercholesterolemia and certain poisonings. A case can also be made for its use in certain other autoimmune diseases when they are refractory to conventional treatment.
Plasmapheresis undoubtedly exerts an immunosuppressive effect, but is seldom safe to use alone because of the tendency to produce rebound with overshoot of antibody levels. It is usually used together with immunosuppressive drugs. Some have suggested that these are synergistic but this is unproven. The great advantage of plasmapheresis is speed so that vulnerable end organs such as the kidney or nerve may be spared from the onslaught of circulating antibody while immunosuppressive drugs are switching off its production. Thus plasmapheresis confers no additional benefit to conventional immunosuppression in cases of rapidly progressive glomerulonephritis with independent renal function, but is of significant benefit for those patients who are already oliguric. In a similar way, plasmapheresis is effective in polyarteritis nodosa associated with hepatitis B virus when combined with antivirals such as vidarabine or interferon a which, in eliminating the antigen, reduce the generation of immune complexes.
The considerable placebo effect of connecting a patient to a whirring machine with flashing lights tended by an attentive nurse should not be underestimated and some have recommended that controlled clinical trials should include a sham apheresis arm. The role of plasmapheresis is becoming clearer as more controlled trials report. Even where a clear role has been previously established new and cheaper methods of immune manipulation may usurp its position. A good example is the use of intravenous immunoglobulin in the Guillain-Barre syndrome.
See also: Cryoglobulin; Goodpasture's syndrome; IgG; IgM; Immune complexes; Immunosuppression; Lymphoma; Neuromuscular junction autoimmunity; Plasma.
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