Using ANA Patterns to Diagnose Autoimmune Disorders

From Medscape Rheumatology > Viewpoints

Kevin Deane, MD

Pattern on the Antinuclear Antibody-HEp-2 Test Is a Critical Parameter for Discriminating Antinuclear Antibody-Positive Healthy Individuals and Patients With Autoimmune Rheumatic Diseases

Mariz HA, Sato EI, Barbosa SH, Rodrigues SH, Dellavance A, Andrade LE
Arthritis Rheum. 2011;63:191-200.
Introduction

Testing for antinuclear antibodies (ANAs) is an important aspect of the clinical evaluation of patients with autoimmune rheumatic diseases (ARDs). Understanding how ANA patterns, titers, and extractable nuclear antigen (ENA) profiles are associated with disease or healthy states can help rheumatologists, as well as other healthcare providers, better utilize ANA testing to accurately identify disease. In this study, the authors evaluated the features of ANA testing that discriminated between healthy individuals and those with ARDs.

Study Summary

In Brazilian patients with a variety of known ARDs (N=138; 87 with systemic lupus erythematosus, 45 with systemic sclerosis, 11 with Sjögren syndrome, and 10 with inflammatory myopathy) and healthy controls (N=118), the authors evaluated ANA titers and patterns using indirect immunofluorescence (IIF) with HEp-2 cells as antigen. Additionally, in these groups, the authors tested for autoantibodies to the ENAs Sm, U1 RNP, SSA, and SSB using Ouchterlony methodology, and for antibodies to double-stranded DNA using the Crithidia luciliae assay.

The authors found that an ANA titer of 1:80 was 90.2% sensitive and 87.1% specific for an ARD; a titer of 1:1280 was 65.4% sensitive and 97.9% specific for an ARD. Also, the ANA patterns of nuclear homogeneous, coarse speckled, and centromeric were highly specific for patients with ARDs, while the nuclear dense fine speckled pattern only appeared in healthy individuals (this latter pattern was associated with a 75kd antigen on Western blot). Antibodies to ENAs were highly specific to patients with ARDs; anti-SSA positivity was present in only 1 healthy individual. Additionally, a subset (N=41) of the healthy individuals who were initially positive for ANA (> 1:80) with an IIF appearance of a dense fine speckled pattern were evaluated 4 years after initial testing, and none had developed an ARD.

The authors concluded that on ANA testing with IIF, the titer and pattern were helpful in discriminating between disease and healthy states.

Viewpoint

In the United States and elsewhere, there is increasing popularity of ANA testing by high-throughput methodologies such as ELISA or array-based assays that do not identify ANA patterns, even though there are concerns that these newer methodologies may lack the diagnostic accuracy for ARDs of IIF testing.[1] Although there are some flaws with this paper, the findings presented support that providing ANA testing by IIF may yield valuable clinical information, and, therefore, healthcare providers who evaluate patients with suspected ARDs may lose valuable clinical information if IIF testing is completely abandoned. As an editorial that accompanies this article points out,[2] the authors of this paper could have provided valuable data to inform the ongoing debate about which methodology for ANA testing is optimal for the identification of ARDs if comparison testing between ANA methodologies were performed. Going forward, such direct comparisons are crucial to allow providers to make the best decisions regarding which type of ANA testing methodology to use in clinical practice.

abstract

OBJECTIVE: To identify features of antinuclear antibody (ANA)-HEp-2 test results that discriminate ANA-positive healthy individuals and patients with autoimmune rheumatic diseases (ARDs).

METHODS: We sequentially retrieved data on 918 healthy individuals and 153 patients with ARDs after clinical assessment. ANA-positive healthy individuals for whom data were available were reevaluated after 3.6-5.0 years. An ANA-HEp-2 test result was considered positive when a clear ANA pattern was observed at 1:80 dilution in 2 distinct commercial HEp-2 slides by 2 blinded independent observers.

RESULTS: ANAs were present in 118 healthy individuals (12.9%) and 138 patients with ARDs (90.2%). The ANA titer was higher in patients with ARDs than in healthy individuals (P<0.001). The ANA pattern profile was distinct in the 2 groups. Nuclear homogeneous, nuclear coarse speckled, and nuclear centromeric patterns appeared exclusively in patients with ARDs. The nuclear dense fine speckled pattern occurred only in healthy individuals. The most frequent ANA pattern in both groups was the nuclear fine speckled pattern, which occurred at lower titer in healthy individuals than in patients with ARDs (P<0.001). Anti-extractable nuclear antigen was present in 1 healthy individual (anti-SSA/Ro) and in 52 patients with ARDs (37.7%). None of the 40 reevaluated healthy individuals developed ARDs, and 29 (72.5%) remained ANA positive. All healthy individuals who became ANA negative had an ANA titer of 1:80 at baseline.

CONCLUSION: Our findings suggest that the titer, and especially the pattern, on the ANA-HEp-2 test strongly enhances our ability to discriminate ANA-positive healthy individuals and patients with ARDs.