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Infliximab in Autoimmune Disease
Infliximab is a chimeric (mouse/human) anti-tumor necrosis factor (TNF)-alpha monoclonal antibody. Therapy with monoclonal antibodies like infliximab has revolutionized therapy in patients with immune diseases such as inflammatory bowel disease (Crohn’s disease [CD] and ulcerative colitis [UC]), rheumatoid arthritis and psoriasis. These agents are generally given to patients who fail conventional medical therapy, and they are typically highly effective for induction and maintenance of clinical remission. However, not all patients respond, and a high proportion of patients lose response over time. An estimated one-third of patients do not respond to induction therapy (primary nonresponse), and among initial responders, response wanes over time in approximately 20% to 60% of patients (secondary nonresponse). The reason for therapeutic failures remains a matter of debate. One proposed factor associated with loss of response is the production of antidrug antibodies, which accelerate clearance of the drug. Antibodies to infliximab have also been associated with acute infusion reactions and delayed hypersensitivity to infliximab. 

Detection of Antidrug Antibodies
The detection and quantitative measurement of anti-infliximab antibodies, also referred to as human antichimeric antibodies (HACA) or antibodies to infliximab (ATI), has been fraught with difficulty. First-generation assays, (i.e., enzyme-linked immunoabsorbant assays [ELISA]) can only measure antidrug antibodies in the absence of detectable drug levels due to interference of the drug with the assay, limiting clinical utility. Other techniques available for measuring antibodies include the radioimmunoassay (RIA) method, and more recently, the homogenous mobility shift assay (HMSA) using high-performance liquid chromatography.

Disadvantages of the RIA method are associated with the complexity of the test and prolonged incubation time, and safety concerns related to the handling of radioactive material. The HMSA has the advantage of being able to measure antidrug antibodies when infliximab is present in the serum. Studies evaluating the validation of the results between different assays are lacking, making interstudy comparisons difficult.

Treatment Options for Patients with Secondary Loss of Response to Infliximab
A diminished or suboptimal response to infliximab can be managed in several ways: shortening the interval between doses, increasing the dose, switching to a different anti-TNF agent (in patients who continue to have loss of response after receiving the increased dose), or switching to a non-anti-TNF agent. 

Prometheus® Laboratories Inc. offers an ELISA-based test for the measurement of serum infliximab and human antichimeric antibodies (HACA). This test is set to be discontinued in August 2012 and replaced with an HMSA called the Anser™IFX test. The Anser IFX test is not ELISA-based and can measure antibodies to infliximab in the presence of serum infliximab, improving upon a major limitation of the ELISA method. Anser IFX is offered as a combined test measuring serum concentrations of infliximab and antibodies to infliximab. 

This test was developed and its performance characteristics determined by Prometheus Laboratories Inc. It has not been cleared or approved by the U.S. Food and Drug Administration. Prometheus Laboratories Inc. is a CAP-accredited Clinical Laboratory Improvement Amendment (CLIA) laboratory. 

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

Non-Covered Codes

This is not an all-inclusive list of non-covered procedure codes.

All codes billed for this procedure are considered investigational and not eligible for coverage. 

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