ANA 11 Components (No ANA Screen)

Anti-dsDNA antibodies arise from dysregulated B-cell tolerance and target the phosphodiester backbone of double-stranded DNA, forming pathogenic immune complexes that deposit in glomeruli and other tissues, driving complement activation and organ inflammation. Titre levels fluctuate dynamically with lupus disease activity, distinguishing anti-dsDNA from most other panel components which remain stable once positive.

Anti-dsDNA IgG is one of two autoantibodies included as a weighted domain in the 2019 EULAR/ACR SLE classification criteria. Rising titres correlate with lupus nephritis activity and can precede clinical flare, providing actionable serial monitoring data in established SLE in a way that most other CTD autoantibodies do not.

Smith antibodies target the B, B', D, E, F, and G polypeptide components of snRNP (small nuclear ribonucleoprotein) complexes within the spliceosome, typically arising through epitope spreading from an initial U1-RNP response. Once established, anti-Sm titres remain stable regardless of disease activity.

Anti-Sm carries approximately 99% specificity for SLE, making it the most diagnostically specific component in the panel, though sensitivity is low at 20–30%. A positive result is diagnostically significant regardless of titre level and supports SLE classification per EULAR/ACR criteria. Anti-Sm does not correlate with disease activity and is not used for monitoring.

Anti-U1-RNP antibodies target the 70 kDa, A, and C protein components of the U1 small nuclear ribonucleoprotein complex involved in pre-mRNA splicing. They represent a distinct B-cell response from anti-Sm despite shared snRNP substrate and are present across multiple connective tissue disease diagnoses.

High-titre anti-U1-RNP is the defining serological criterion for mixed connective tissue disease (MCTD), present in over 95% of cases. It is also found in SLE, systemic sclerosis, and overlap syndromes. Isolated high-titre anti-RNP without other CTD-specific antibodies should prompt clinical assessment specifically for MCTD.

The Ro60 antigen is a cytoplasmic and nuclear RNA-binding protein involved in RNA quality control and surveillance of misfolded non-coding RNAs. Anti-Ro60 antibodies are among the most prevalent autoantibodies in systemic autoimmune rheumatic disease and can cross the placenta with direct foetal consequences.

Anti-Ro60 is the primary SSA marker for primary Sjögren's syndrome (present in 70–90% of cases) and is also found in SLE. It carries critical obstetric significance — maternal anti-Ro60 is associated with neonatal lupus erythematosus and congenital heart block, necessitating serial foetal cardiac surveillance by Doppler echocardiography from approximately 16 weeks of gestation in seropositive pregnancies.

Ro52 (TRIM21) is an E3 ubiquitin ligase involved in innate immune regulation and is a structurally and functionally distinct protein from Ro60, despite the shared SSA designation. It is not an RNA-binding protein and is not part of the canonical Ro ribonucleoprotein particle, making the two SSA antigens immunologically non-redundant.

Anti-Ro52 is found in Sjögren's syndrome and SLE but has a distinct additional association with inflammatory myopathies, where it co-occurs with antisynthetase antibodies and is independently associated with interstitial lung disease. Isolated anti-Ro52 positivity without anti-Ro60 should prompt evaluation for myositis-spectrum disease alongside Sjögren's, not Sjögren's alone.

The La (SS-B) antigen is an RNA-binding phosphoprotein that associates with RNA polymerase III transcripts and plays a role in RNA processing and transcription termination. Anti-SSB/La antibodies arise through epitope spreading and are almost invariably present alongside concurrent anti-SSA/Ro positivity.

Anti-SSB/La is highly associated with primary Sjögren's syndrome and is rarely present in the absence of anti-SSA/Ro. The co-occurrence of both anti-SSA and anti-SSB confers higher neonatal lupus risk than anti-SSA alone. Isolated anti-SSB without anti-SSA is clinically uncommon and warrants confirmatory repeat testing to exclude a false-positive result.

Anti-Scl-70 antibodies target DNA topoisomerase I, a nuclear enzyme that relieves torsional strain in DNA during replication and transcription. They are detected by ELISA or line blot immunoassay and are generated against the intact enzyme and its proteolytic fragments.

Anti-Scl-70 is the serological hallmark of diffuse cutaneous systemic sclerosis (dcSSc) and carries strong prognostic significance — positive patients have substantially elevated risk of pulmonary fibrosis and interstitial lung disease. It is rarely co-positive with anti-centromere B, with the two antibodies largely defining divergent SSc disease subsets.

Jo-1 antibodies target histidyl-tRNA synthetase (HRS), a cytoplasmic aminoacyl-tRNA synthetase responsible for charging histidine onto its cognate tRNA during protein synthesis. Anti-Jo-1 is the prototype and most prevalent of the antisynthetase antibodies, which as a class define antisynthetase syndrome.

Anti-Jo-1 is the defining autoantibody of antisynthetase syndrome — characterised by the clinical pentad of inflammatory myopathy, interstitial lung disease, inflammatory arthritis, mechanic's hands, and Raynaud's phenomenon. A positive result warrants pulmonary function testing and HRCT chest to screen for ILD, which is the primary driver of morbidity and mortality in this condition.

Centromere B (CENP-B) is a constitutive kinetochore protein of 80 kDa that binds to a specific 17-base pair sequence in centromeric satellite DNA and is essential for proper chromosome segregation during mitosis. Anti-CENP-B antibodies are the primary marker used clinically as a surrogate for anti-centromere reactivity and are detected by ELISA or line blot.

Anti-centromere B is the characteristic serological marker for limited cutaneous systemic sclerosis (lSSc), including CREST syndrome, with specificity approaching 98% for systemic sclerosis. Positive patients carry elevated risk of pulmonary arterial hypertension relative to anti-Scl-70-positive patients. Anti-centromere and anti-Scl-70 are mutually exclusive in the vast majority of cases, defining divergent SSc subsets.

Histone antibodies target the core nucleosomal histone proteins H2A, H2B, H3, and H4, as well as linker histone H1, generated through mechanisms including impaired apoptotic clearance of nucleosomal material and drug-induced disruption of central tolerance.

Anti-histone is present in over 95% of drug-induced lupus erythematosus (DILE) cases, making it the key discriminating marker when this diagnosis is considered. Causative agents include procainamide, hydralazine, minocycline, isoniazid, and TNF-alpha inhibitors. Anti-histone is also found in approximately 50–70% of idiopathic SLE — drug history is essential for interpretation and positivity alone cannot distinguish DILE from idiopathic SLE.

Anti-chromatin antibodies target the intact nucleosome — the fundamental chromatin unit comprising approximately 147 base pairs of DNA wrapped around a histone octamer — representing a distinct immune response from anti-dsDNA or anti-histone targeting of individual nucleosomal components.

Anti-chromatin is found in 50–80% of SLE cases and is included as a weighted biomarker domain in the 2019 EULAR/ACR SLE classification criteria, providing additive diagnostic sensitivity alongside anti-dsDNA, particularly in anti-dsDNA-negative patients. It is also associated with drug-induced lupus; serial monitoring has limited utility as titres do not consistently track disease activity.