New Diagnostic Test Has High Specificity for Early-Stage Arthritis

The FDA has approved the first fully automated assay for measuring cyclic citrullinated peptide (CCP) antibodies, a relatively new serologic marker that is now considered a useful and highly specific marker for the early diagnosis of rheumatoid arthritis (RA).

By identifying RA in its earliest stages, the EliA CCP assay (Phadia US) will allow physicians to initiate aggressive treatment with agents that are often more effective during the nascent stages of disease. This can significantly reduce the risk of the disease progressing to irreversible joint damage.

Ann N Y Acad Sci

The benefit of CCP testing has been demonstrated in several studies, including a recent analysis of 700 consecutive serum samples from patients seen at outpatient clinics (. 2005; 1050:314-318).

Compared with the traditional approach of determining the presence of rheumatoid factor, anti-CCP reactivity was more sensitive (74.0% for anti-CCP vs 69.7% for rheumatoid factor) and much more specific (94.5% vs 69.7%). Since tests for rheumatoid factor also yielded more false-positive results, the authors concluded that anti-CCP can also be helpful in diagnosing other inflammatory and noninflammatory conditions, particularly connective tissue diseases, including systemic lupus erythematosus and Sjögren’s syndrome.

The availability of the EliA CCP assay “will offer healthcare providers a more accurate tool to diagnose this debilitating condition at an early stage in the disease compared with older testing methods,” said Michael Land, president of Phadia US. He described it as “an economical and automated test with new levels of precision, sensitivity, and specificity.”

The test is covered by Medicare and many other payers; the Medicare payment is $18.09. Since it is a routine immunoassay, results will typically be available within 24 to 48 hours. However, in rural areas where samples must be sent to a distant reference laboratory, the turnaround time may be longer.

Despite its novelty, the EliA CCP assay is currently available in all major reference labs, and thus is essentially on the menu in all US labs. With growing demand, additional labs are expected to include it as a routine in-house test.

About 2.1 million people in the United States have RA, making it the most common inflammatory joint disease, according to the National Institutes of Health (NIH). The disease is characterized by symmetric, erosive joint synovitis, resulting in pain, stiffness, and swelling. Without treatment, patients may eventually lose joint function. The NIH projects that by the year 2020, 60 million people in the United States will have arthritis or other rheumatic conditions.

For more information, call Phadia US at 800-346-4364.