Antinuclear Antibodies

What are antinuclear antibodies (ANA) ?

ANA are IgG antibodies against intracellular components of human cells. Both nuclear and cytoplasmic staining patterns are reported. Patient serum, diluted 1:40, is incubated with HEp2 cells and then fluorescent anti-IgG antibodies are added to detect any patient antibodies which have bound to HEp2 cells. For every new sample, if staining is seen the serum is titrated to determine the final titre. What is reported is the pattern and the titre (ie the dilution where the staining was still visible).

Examples of typical staining patterns can be seen in our fluorescence image library.

When should ANA be requested?

One of the problems with ANA is that up to 20% of the population have low/medium titre (i.e. 1:40 - 1:400), particularly in people over the age of 50 and also in children. Further more ANA also appear transiently following major or minor illness. The specificity of the test therefore reflects the clinical picture of the patient and are most useful in patients with suspected autoimmune disease. 

What does a positive ANA mean?

Low titre ANAs (ie 1:40 or 1:100) are usually not clinically relevant whereas high titre ANA (particularly 1:1600) are infrequent amongst healthy individuals and so therefore carry a greater clinical significance. Below is a table of common ANA patterns and their clinical association. Possibly the most important use is to exclude SLE.

Summary of ANA associated clinical conditions

 

ANA
Pattern  Cell target  Disease Association
Nuclear staining
Homogeneous
dsDNA SLE (95%), Discoid Lupus, Autoimmune Hepatitis
Rheumatoid Arthritis 
Histones SLE
Nucleolar  PM-Scl Extensive Scleroderma (30%), Polymyositis/Scleroderma overlap syndrome
Primary Pulmonary Hypertension
Nuclear Matrix hRNP Mixed Connective Tissue Disease, SLE
Speckled - fine SS-A (Ro)
SS-B (La) 
Sjogren's Syndrome (95%), SLE (40%), Scleroderma (5%)
Speckled - coarse SnRNP SLE, SLE overlap Syndromes
Centromere CENT A-E Limited Scleroderma / CREST (60%), Raynaud's Phenomenon
Proliferating Cell Nuclear Antigen (PCNA  Cyclin  SLE (1-3%) - often associated with glomerulonephritis 
Nuclear Dots p80 coilin  Autoimmune and viral liver disease  
Cytoplasmic staining
Fine Speckled Jo-1 Polymyositis (20-40%)
Ribosomal Pattern Ribosome P SLE (10-15%)
Mitochondrial M2 Primary Biliary Cirrhosis (90%), Scleroderma (40%)
ER CytochromeP450 Drug Induced Hepatitis
Golgi Various SLE (rare), Sjogren's Syndrome
Cytokeratin Cytokeratin Rheumatoid Arthritis (30-80%), Mixed Connective Tissue Disease, Autoimmune Hepatitis, Crohn's Disease, Squamous Cell Carcinoma of Lung