Lupus Lab Tests Explained: What Blood Tests Mean for Diagnosing and Monitoring Lupus

Key lupus lab tests include CBC, metabolic panel, urine protein:creatinine, ANA, anti-dsDNA, anti-Smith, complement levels (C3, C4), anti-C1q, EC4d (from Exagen labs), and urinalysis. These help diagnose lupus, monitor disease activity, and detect organ involvement like lupus nephritis

Over 200 genes have been discovered that increase the risk of getting lupus. However, it takes triggers (like UV light, smoking, mononucleosis infection, lack of sleep, stress, and many more) to “turn the genes on,” causing the immune system to turn against the person’s own body. Family members of people who have autoimmune diseases are at greater risk of developing lupus. Fortunately, there are things they can do to lower their risk of lupus: https://www.lupusencyclopedia.com/how-to-prevent-lupus/

Yes, you can have lupus and be ANA negative. This can occur for several reasons, including that particular lab test was not sufficient to identify your ANA, fluctuations of ANA over time, and in people with well treated lupus. See my blog post here: https://www.lupusencyclopedia.com/yes-you-can-be-ana-negative-and-have-lupus/

I like to check labs every 3 months, especially checking the urine protein:creatinine ratio to ensure my patient doesn’t develop lupus nephritis. If they do, I want to treat it ASAP. Labs should also be followed to see how well someone’s lupus responds to therapy and ensure we are treating them adequately. Another reason to follow labs is to ensure someone doesn’t develop side effects to the medications.

If the C3 and C4 decrease in a patient during disease activity, then increase with treatment, this usually means that these labs can be helpful in monitoring disease activity and responses to therapy. However, this doesn’t occur in everyone.  During inflammation, the liver makes a lot more C3 and C4. Therefore, this can balance out the decreasing C3 and C4 that occurs during lupus immune system activity, making these tests unhelpful in around 80% of patients. Fortunately, there is a better measurement of complement from the lab called Exagen, called EC4d, that is included in their SLE Monitor test.

Traditionally considered stable, recent studies suggest that anti-Smith and anti-RNP antibodies may fluctuate with lupus activity in some patients, though more research is needed.