Background/Purpose: Autoimmune systemic rheumatic disease (SARD) diagnostic approach is complex and recently there are some diagnostic tools to rule-out autoimmune disease diagnoses. ANAS/DFS70 antibodies have attracted interest as a positive result in patients without clinical evidence of SARD, but we are scarce on data validation in Latin American countries population. The objective of this study was to  assess  ANA/DFS70  performance  in  a  large  population  with  SARD compared  with  first  degree  relatives and  healthy controls.

Methods: A cross-sectional study was conducted. We analyzed 531 individuals between 18-65 years old,  101 early rheumatoid  arthritis  (eRA)  patients  (ACR/EULAR  2010  classification  criteria), 137 first degree relatives (FDR) from  RA,  60  psoriasis (Ps)  patients  (Colombian  classification consensus),  47 Undifferentiated connective tissue diseases (UCTD) patients and 186 healthy controls matched by age and sex. The healthy control group were individuals who lived and work similarly like those  patients  those  criteria  of  exclusion  criteria  were  to  present  autoimmune  or  auto-inflammatory  disease,  infectious,  neoplasms,  diabetes,  antibiotic  treatment,  pregnancy  or lactation, consanguinity with autoimmune entities.

The  determination  of  ANA-HEp2  antibodies  (ANA-Hep-2  AESKU.Dignostic®,  Autoantiboy test SYSTEM IMCO DIAGNOSTICS REF 1103® and ANA-Hep-2 AESKU.Dignostic®) was carried  out.  The  positive  results  (standard  AC-2)  are  used  as  a  confirmatory  test  the determination  of  ANAS  /  DFS70:  AUTOANTIBOY  TEST  SYSTEM  IMMCO  DIAGNOSTICS (Knocked out, for the psip gene) REF 1108® and CytoBead ANA Generic Assays ref 8065 ® by indirect immunofluorescence-IFI technique (Figure 1). In addition, serum levels of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), IgG/IgA antibodies against citrullinated peptide (ACPA), and rheumatoid factor (RF). Absolute and relative frequencies were established.

Results: 531 participants were included: eRA 19%, 25,8% RA FDR, Ps 11,3%, UCTD 8,9%, and 35% healthy controls. eRA mean age was 41,8±12,2 years, female 82,2%, with ANA test(+) result 42%. In Ps mean age 49,1±15,7 years, female 53,3%, ANA test(+) 41,7%. UCTD mean age 41,3±15,2 years, female 85,1%, and ANA test(+) 78,7%. RA FDR mean age 38,7±12,2 years,  female  73%,  ANA  test(+)  26,3%.  And  healthy  controls  mean  age  41,3±12,2  years, female 74,7%, and ANA test(+) 26,9%. ANA/DFS70 was positive in a 6,4% in UCTD, 3,2% in healthy controls, 1,7% in Ps, 1,5% in RA FDR, no eRA had positive results (Figure 2). These 12 participants were negative for acute phase reactants (ESR[-] 83,3% and CRP[-] 66,6%), as well as they were all negative for RF and two were positive for APCA  from UCTD.

Conclusion: ANAS/DFS70 autoantibodies were present in very low frequency in patients with SARD, specially no eRA patient had a positive test result. Thus, patients with a positive result tend to have a mild or non-progressing phenotype of SARD, as UTCD. This is the first time ANA/DFS70 are tested in a large population cohort in Latin American countries which coincide with previous results in RA and RA relatives.

Figure 1. Indirect immunofluorescence for ANA: A: Postive Cytobeads ANA for DFS70, B: positives control beads for cytobeads, C: ANA: AC-2 – Nuclear dense fine speckled (Speckled pattern distributed throughout the interphase nucleus with characteristic heterogeneity in the size and D: ANA: AC-0 – Negative.

Figure 2. Participants were RA 19%, 25,8% RA first degree relatives, Ps 11,3%, UCTD 8,9%, and 35% healthy controls. ANA/DFS70 was positive in a 6,4% in UCTD, 3,2% in healthy controls, 1,7% in Ps, 1,5% in relatives of RA, no RA had positive results.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/low-frequency-of-ana-dfs70-pattern-positive-result-in-a-large-cohort-of-autoimmune-autoinflammatory-diseases-compared-with-first-degree-relatives-and-healthy-controls-evaluated-in-a-single-hospital-fr/