The test for psoriatic arthritis reports the presence or absence of a specific variation in the immune response gene, MICA. It is thought that MICA functions as a stress-induced antigen that is broadly recognized by epithelial gamma delta T cells. Test material is collected using a cheek swab and analyzed in a Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory.

MICA encodes the highly polymorphic MHC (HLA) class I chain-related gene A. The protein product is expressed on the cell surface, although unlike canonical class I molecules, does not seem to associate with beta-2-microglobulin. A specific variation on the MICA immune response gene is located on chromosome 6. In particular, a variant called MICA-A9 is found in approximately 60% of patients who develop PsA.

The genetic test, called PsoriasisDX, is provided by DermaGenoma, Inc., (PsoriasisDX LLC, Irvine, CA, USA). The PsoriasisDX genetic screening test reports on the presence or absence of the MICA-A9 allele. According to the published studies, a patient with a positive test result has approximately 60% chance of developing PsA, while a patient with a negative test result has approximately 70% chance of not developing PsA. Diagnosis is often complicated by overlapping symptoms with other arthritic conditions, as well as variable disease expression across patients; therefore, it is possible that the prevalence of PsA among psoriasis patients far exceeds current estimates.

Scientists believe that psoriasis and PsA share common susceptibility genes, since a significant proportion of psoriasis patients and their first-degree relatives develop PsA. Given that the immune system is involved in the pathogenesis of both diseases, it is not surprising that variations in immune response genes have shown the strongest association with psoriasis and PsA. The need for early screening and medical intervention for PsA is underscored by the fact that PsA becomes more severe when left untreated, leaving patients with significant joint damage.

Andy Goren, president and CEO of PsoriasisDX, LLC noted that PsoriasisDX is now available as a CE (Conformité Européenne) marked product under the European In Vitro Diagnostic Directive and added, "We are excited to extend this revolutionary genetics testing breakthrough to dermatologists in Europe."

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DermaGenoma, Inc.