Lupus is a tricky disease to diagnosis because its signs and symptoms mimic those of so many other diseases. In fact, when health care professionals walk down the path toward lupus diagnosis, they first take into consideration three factors about a patient:
- His or her complete medical history
- An analysis of results obtained in routine laboratory tests
- Results from specialized tests related to immune status
One of the most common tests used by physicians to help diagnose lupus is the anti-nuclear antibody (ANA) blood test.
The ANA test is a screening test used for several autoimmune diseases. It determines whether auto-anitbodies to cell nuclei are present in a person’s bloodstream.
The ANA is currently one of the most sensitive diagnostic tests available for confirming the diagnosis of SLE when accompanied by typical clinical findings. Without those findings, however, a positive ANA may mean nothing at all.
The Elusive Positive ANA:
In 97% of cases diagnosed as SLE, those patients will produce a positive ANA. But a positive ANA test result must be accompanied by more common clinical features, such as ailments of the skin, joints, kidneys, central nervous system, and so forth, to truly signal SLE. And further testing is almost always required to make a final diagnosis.
Also, a positive ANA test by itself could be one of several other diseases, including drug-induced lupus. Some of those diseases include:
- Other connective tissue diseases, such as scleroderma and rheumatoid arthritis
- Reaction to certain drugs
- Viral illnesses, such as infectious mononucleosis
- Chronic infectious diseases, such as hepatitis and malaria
- Other autoimmune diseases, including thyroiditis and multiple sclerosis
Overall, the ANA test should be considered a screening test. A positive test without clinical features or other signs or symptoms of lupus can often be dismissed by the patient.