Research Reveals Potential New Noninvasive Lupus Test

Receiving a diagnosis for systemic lupus erythematosus (SLE) can take about 6 years after symptoms start. This is because SLE is difficult to diagnose.¹

Doctors rely on several tests, symptoms, and what they can see to make a diagnosis. Tests sometimes involve imaging. But they usually involve analyzing urine and blood.²

While blood tests are quick and effective, not everyone likes getting pricked. Fear of needles can even lead some people to avoid medical tests. This is 1 of the reasons researchers have been looking for other ways to screen and test for SLE.³

A new way of testing for lupus

New research shows that saliva can be used to test for SLE. The study looked for biological substances in saliva that are linked to disease activity. These substances are called biomarkers.^4,5

Collecting saliva is less invasive than collecting blood. But it can take longer. In the study, it took about 15 minutes to collect enough saliva to test. The study also looked at biomarkers in urine.⁵

Eight different biomarkers were tested in people with and without SLE. All of the biomarkers signal inflammation. Of people in the study who had SLE, some had kidney damage, and others did not.⁵

The researchers found that 4 of the biomarkers were present at higher levels in saliva when the people with SLE had healthy kidneys. These biomarkers were:⁵

• Colony-stimulating factor-1
• Tumor necrosis factor-α (TNF-α)
• Interferon-γ-induced protein-10 (IP-10)
• Monocyte chemoattractant protein-1 (MCP-1)

But people with SLE who also had kidney damage had higher levels of TNF-α, IP-10, and MCP-1 in their urine than in their saliva. (These 3 are also reliably found in people with several different kinds of diseases where the immune system attacks the body.)⁵

This means that collecting saliva and urine is a good alternative to collecting blood for helping to diagnose SLE.⁵

Limitations to the study

A few things in the study deserve a closer look. First, when patients had high levels of disease activity, the researchers found higher levels of the biomarkers in their saliva. But when people with SLE had disease activity mostly in their kidneys, testing urine usually gave better information than testing saliva. For now, this just means that samples of each may be needed for a test.⁵

Second, the study did not include people who have Sjögren’s syndrome as a secondary condition to SLE. Sjögren’s syndrome impairs the saliva glands and causes dry mouth. It is not clear how this condition would affect using saliva for testing.⁵

Third, some of these biomarkers are also present in people’s saliva when they have periodontitis (their gums are severely infected). For people who have periodontitis, a saliva test alone could not be used to diagnose SLE.⁵

Fourth, this new method of detecting biomarkers in saliva and urine will not be available immediately. Researchers may still need to pinpoint what level or range of these biomarkers indicates SLE. And the Food and Drug Administration would need to approve a new diagnostic test.

But 1 future day, saliva and urine tests may be viewed as equal to blood tests.

Current tests for lupus

For now, diagnosing lupus involves a combination of symptoms and blood tests.

Symptoms may include:⁶

• A butterfly-shaped rash over the cheeks and nose
• Skin rash from sun exposure
• Red, raised, oval, or round rash
• Mouth or nasal sores
• Tenderness, swelling, or pain in 2 or more joints
• Lung or heart inflammation
• Kidney problems
• Neurological problems

A few other signs may show up in blood tests, including low blood cell counts of:⁶

• Red blood cells
• White blood cells
• Platelets
• Certain abnormal antibodies
• Antinuclear antibodies

In most cases, a negative antinuclear antibody test means you do not have lupus. But a positive test and multiple symptoms means you might. In this case, you may need more tests. About 97 percent of people who have a positive test for antinuclear antibodies are diagnosed with lupus.^6,7

In very rare cases, people have a negative antinuclear antibody test and still have lupus. These people may have other antibodies.⁸

Your doctor may also order tests to look for protein in your blood, or protein or blood in your urine. Or, your doctor may also need images of your heart or chest to see if your lungs and heart are healthy.^7,9