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AB1006 Anti-Citrullinated Peptide Antibodies and Rheumatoid Factor Testing Patterns among Patients with Rheumatoid Arthritis in The US
  1. J. An1,
  2. A. Lin2,
  3. Z. Bider3,
  4. E. Alemao4,
  5. S.E. Connolly4,
  6. T.C. Cheetham3
  1. 1Western University of Health Sciences, Pomona
  2. 2Southern California Permanente Medical Group, Fontana
  3. 3Southern California Permanente Medical Group, Pasadena
  4. 4Bristol-Myers Squibb, Princeton, United States

Abstract

Background Serological markers have been investigated for the identification of RA. Current diagnostic criteria recommend conducting tests for anti-citrullinated peptide antibodies (ACPA) and rheumatoid factor (RF) prior to reaching the RA diagnosis. However, there is a lack of information about how these tests are utilized in a managed care setting.

Objectives To describe the frequency of ACPA/RF tests at the time of RA diagnosis and at follow-up, as well as to compare baseline characteristics between patients who received ACPA/RF tests and those who did not.

Methods A cohort study was conducted using adult patients newly diagnosed with RA within a US integrated healthcare delivery system from 1 January 2007 to 31 December 2014. Individuals were followed from their first RA diagnosis (index date) until 30 June 2015. Patients were required to have two ICD-9 codes of 714.x, treatment with a DMARD, and continuous eligibility for 12 months prior to the index date (baseline period). At baseline, data were collected on co-morbid conditions, laboratory test results and dispensed medications. Descriptive statistics and multivariable logistic regression analyses were conducted to describe ACPA/RF testing patterns and to investigate baseline patient characteristics associated with ACPA/RF testing.

Results A total of 7444 patients with newly diagnosed RA were identified. Mean (SD) age was 55.6 (15.0) years, 75% were female, 69% of patients received corticosteroid treatment and 22% had other autoimmune diseases at baseline. Overall, 83% had both ACPA and RF tests at baseline while 10% and 2% had only an RF or an ACPA test, respectively. Baseline ACPA and RF testing rates were increased over time (p<0.001) and both ACPA and RF testing rates were >90% from 2012 onwards (Table). At baseline, 34% of patients had positive ACPA and RF test results, 30% had negative ACPA and RF results, 6% had only ACPA-positive and 21% had only RF-positive results. During follow-up, 20% of patients repeated their ACPA tests; 11% had a repeat test within 1 year of baseline. Patients with a higher Elixhauser index (odds ratio [OR]=0.72, 95% CI 0.62, 0.95) were less likely to receive ACPA tests at baseline, whereas patients receiving NSAIDs (OR=1.45, 95% CI 1.25, 1.69) or corticosteroids (OR=1.23, 95% CI 1.07, 1.43) were more likely to receive baseline ACPA tests. Patients who had other autoimmune conditions were more likely to repeat their ACPA tests during follow-up.

Table 1.

Baseline ACPA and RF testing rates by index year

Conclusions ACPA and RF testing rates in patients with RA have increased over time, with 96% of patients with newly diagnosed RA receiving both tests at the time of RA diagnosis in 2014. However, there may be still discrepancies in testing based on co-morbidities and medications. The reasons why RF or ACPA tests were not conducted in some patients with RA remain to be identified.

  1. Aletaha D, et al. Ann Rheum Dis 2010;69:1580–8.

Disclosure of Interest J. An Grant/research support from: Bristol-Myers Squibb, A. Lin Employee of: Kaiser Permanente, Z. Bider Employee of: Kaiser Permanente, E. Alemao Shareholder of: Bristol-Myers Squibb, Employee of: Bristol-Myers Squibb, S. E. Connolly Shareholder of: Bristol-Myers Squibb, Employee of: Bristol-Myers Squibb, T. C. Cheetham Grant/research support from: Bristol-Myers Squibb

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