Can a Positive ANA Test and Negative DSDNA Test Indicate Lupus?

Diagnosing lupus can be a complex process, sometimes taking years. Although a positive ANA (Antinuclear Antibody) test and a negative DSDNA (Double-Stranded DNA) test may raise suspicion of lupus, other factors and a broader range of symptoms come into play. In this article, we will explore what such a test result might mean and why a comprehensive diagnosis is necessary.

The Complexity of Diagnosing Lupus

Taking between 5 to 25 years, many individuals receive a positive diagnosis of lupus after experiencing a range of symptoms. Even with a positive ANA titer and multiple other symptoms, the diagnostic journey can be long and challenging. In my own experience, I was finally diagnosed and put on medication to control my condition after 25 years. However, my case is unique because I was diagnosed with limited cutaneous systemic sclerosis, also known as scleroderma. Despite its rarity and the limited knowledge of my doctors, I advocate for finding a knowledgeable rheumatologist who can provide the proper diagnosis and treatment.

Criteria for Diagnosing Lupus

According to the American College of Rheumatology (ACR), a positive ANA does not automatically indicate lupus. Lupus is a multifaceted condition, and no single finding is sufficient for a diagnosis. Instead, the ACR has established certain establishment criteria that must be met. For a classification of lupus, a patient must exhibit four or more of the following criteria:

Malar rash Discoid rash Photosensitivity Development of a rash after sun exposure Oral or nasal ulcers Arthritis of multiple joints Serositis: inflammation of the lining around the lungs or heart Kidney disease, indicated by protein or casts in the urine Neurological disorders such as seizures and psychosis Blood disorders such as hemolytic anemia, leukopenia, and lymphopenia

The term classification is not synonymous with diagnosis. A diagnosis of lupus typically requires a greater level of certainty, which is why the ACR criteria are used for research purposes. Despite the criteria being up for review, they are considered to be about 90% effective in diagnosing lupus.

Understanding ANA and DSDNA Tests

While a positive ANA test is common in lupus patients (approximately 98% of those diagnosed), it is important to note that 2% of lupus patients do not have a positive ANA. On the other hand, approximately 20% of individuals without lupus also have a positive ANA test. Additionally, about 30% of lupus patients have anti-double-stranded DNA antibodies, but only 1% of the normal population carries this autoantibody.

The DSDNA test, on the other hand, is more specific to lupus. Only about 1% of the normal population has this autoantibody, but it is found in a much higher percentage of lupus patients. Therefore, a positive ANA and a negative DSDNA test should not be taken as definitive evidence of lupus. Instead, a comprehensive evaluation of symptoms and a variety of test results are necessary for an accurate diagnosis.

Conclusion

Diagnosing lupus is a multi-step process that requires careful consideration of a patient's symptoms and test results. While a positive ANA test and a negative DSDNA test might indicate the presence of lupus, other criteria and symptoms must also be present for a classification of lupus. It is crucial to seek the expertise of a knowledgeable rheumatologist to ensure an accurate diagnosis and effective treatment plan.