Anti ds-DNA Antibody-IFA Test

The ANA or antinuclear antibody test is used to check a person for autoimmune disorders. Autoimmune disorders affect tissues and organs of the body. Systemic lupus erythematosus is the main disorder that ANA testing evaluates. ANA are antibodies produced by a person when the immune system can not differentiate between self and outside entities and they target the body itself. ANA testing can be used with specific testing for further confirmation to diagnose or rule out other autoimmune disorders like Sjögren syndrome, polymyositis and scleroderma.

There are two methods to test for ANA: Indirect fluorescent antibody (IFA): In this method, a person's blood sample is mixed with cells that are affixed to a slide. Autoantibodies that may be present in the blood react with the cells. The slide is treated with a fluorescent antibody reagent and examined under a microscope. The presence (or absence) and pattern of fluorescence is noted. Immunoassays--these methods are usually performed on automated instrumentation but may be less sensitive than IFA in detecting ANA. ANA testing is not used for monitoring SLE in its course hence it is not commonly ordered.

The ANA test is ordered when signs of systemic autoimmune disorder are showcased. The symptoms are vague and not specific, they also change with time and might worsen. Symptoms alternate between flare ups and remissions. Some symptoms include: Low-grade fever Persistent weakness and fatigue Numbness or tingling in the hands or feet Skin sensitivity to light Arthritis-like pain in one or more joints Red rash Hair loss Muscle pain Inflammation and damage to organs and tissues There is also a possibility of a false positive result when ANA exists in an individual but it is not because of an autoimmune disease. A number of drugs and some infections can lead to a positive result. Also, 3-5% of healthy Caucasians may be positive for ANA, which my increase with age to 10-37%.

ANA test is most commonly used to test for SLE. About 95% of those with SLE have a positive ANA test result. This has to be evaluated with subtests and other symptoms of SLE to confirm. Other conditions in which a positive ANA test result may be seen include: Drug-induced lupus: Some medications may trigger this condition. When the drugs are stopped, the symptoms usually go away. Sjögren syndrome: 40-70% of people with this condition have a positive ANA test result. A negative ANA result does not rule it out.

Scleroderma: About 60-90% of those with scleroderma have a positive ANA. In people who may have this condition, ANA subset tests can help distinguish two forms of the disease, limited versus diffuse. The diffuse form is more severe. ANA may occur in people with Raynaud syndrome, arthritis, dermatomyositis or polymyositis and other autoimmune conditions. Since the symptoms of SLE and other autoimmune disorders come and go, a health practitioner must rely on test results, clinical symptoms, and the person's history for diagnosis. A negative ANA result is more or less conclusive, however for confirmation a repeat test might be recommended after some time if symptoms recur. Further sub testing is not required after a negative result.

A simple blood draw is required for testing. The result of an IFA test is reported as a titer, which are ratios. A positive ANA result means autoantibodies are present; however, it is not conclusive. Signs and symptoms along with further evaluation is needed for a final diagnosis. Apart from the titer, a description of the pattern seen is also reported. Different patterns are usually associated with different autoimmune disorders, although there might be overlap.

Some of the more common patterns include: Homogenous (diffuse)—associated with SLE, mixed connective tissue disease, and drug-induced lupus Speckled—associated with SLE, Sjögren syndrome, scleroderma, polymyositis, rheumatoid arthritis, and mixed connective tissue disease Nucleolar—associated with scleroderma and polymyositis Centromere pattern (peripheral)—associated with scleroderma and CREST (Calcinosis, Raynaud syndrome, Esophogeal dysmotility, Sclerodactyly, Telangiectasia)