Date: Monday, November 9, 2015
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose: Anti citrullinated protein antibodies (ACPA) are highly specific for rheumatoid arthritis (RA), but the distribution and diagnostic accuracy of ACPA in general population has not been thoroughly investigated. We aimed to evaluate the distribution and diagnostic accuracy of ACPA in in the general population.
Unselected serum samples from a large population-based twin cohort consisting of 12 590 individuals were analyzed for the presence of ACPA using anti-CCP2 ELISA. All ACPA-positive samples (n=350) were further tested for four peptide-specific ACPAs. C reactive protein (CRP), information on SE and smoking were also available. RA cases were identified by linkage to the Swedish National Patient Register.
Three hundred fifty individuals had a positive ACPA test and 102 of these ACPA-positive individuals had an RA diagnosis at the time of blood donation (prevalent ACPA positive RA). Among the remaining 248 ACPA positive individuals an additional 22 individuals developed RA between blood donation and diagnosis follow-up (incident ACPA negative RA). 53 individuals had an RA diagnosis without testing positive for ACPA at the time of blood donation (prevalent ACPA negative RA) and an additional number of 15 individuals developed ACPA negative RA between blood donation and diagnosis follow-up (incident ACPA negative RA).
Beside smoking and SE, female sex was an important factor associated with ACPA positivity independent of RA diagnosis. The proportion of females was 55% in the entire cohort, 61% among ACPA-positive individuals without RA and 71% among those with prevalent ACPA-positive RA. Female sex was associated with ACPA occurrence (OR=1.6, 95% CI 1.2-2.0) and increased the risk of also having ACPA-positive RA (OR=1.8, 95% CI 1.1-3.1). ACPA-positive individuals without RA had lower ACPA titers and fewer peptide specific ACPAs than both individuals that later developed (incident) ACPA-positive RA and those having prevalent ACPA-positive RA. ACPA-positive individuals had also higher CRP levels than ACPA-negative individuals without RA.
Based on the distribution of ACPA positivity among the 155 cases of prevalent RA at the time point of blood donation, the sensitivity and specificity of ACPA for RA was 66% and 98%, respectively. ACPA high test had a sensitivity of 62% and a specificity of 99%. The positive predictive value (PPV) was 29% (95% CI: 24-34) for ACPA overall, and 48% (95% CI: 41-54) for ACPA high test. The negative predictive values (NPVs) were similar for ACPA test and ACPA high test (99.5% and 99.6 respectively).
ACPAs associate with female sex and have a high diagnostic accuracy for an RA diagnosis in a population setting.
To cite this abstract in AMA style:Hensvold AH, Frisell T, Askling J, Catrina AI. How Well Do Acpas Discriminate and Predict RA in the General Population – a Study Based on 12,590 Population-Representative Swedish Twins [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/how-well-do-acpas-discriminate-and-predict-ra-in-the-general-population-a-study-based-on-12590-population-representative-swedish-twins/. Accessed January 17, 2021.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/how-well-do-acpas-discriminate-and-predict-ra-in-the-general-population-a-study-based-on-12590-population-representative-swedish-twins/