How to Test for Lupus

Lupus is a medical condition with an aura of mystery. Symptoms affect each patient differently and can mimic other disorders. There's no single "lupus test" to pinpoint the disease.

Diagnosing lupus is somewhat like reaching a verdict in a murder trial without an eyewitness, says Dr. S. Sam Lim, a professor of medicine and epidemiology and clinical director of rheumatology at Emory University, and chief of rheumatology at Grady Health System in Atlanta. It's a matter of building on reasonable evidence.

"There are situations where it looks like lupus, it smells like lupus, it talks like lupus and we've ruled out other things," Lim says. In other cases what might look like lupus, is determined to be another medical condition.

[See: 10 Seemingly Innocent Symptoms You Shouldn't Ignore.]

Lupus is one of more than 100 known autoimmune disorders. With these conditions, a person's immune system mistakes the body's own healthy cells for outside invaders, creating auto-antibodies, proteins that target and attack these cells.

Skin rashes, patchy hair loss, fatigue, and joint pain and swelling can raise the suspicion of lupus, particularly in younger women, who are at highest risk. But because systemic lupus erythematosus, the most common form, can affect almost any part of the body, symptoms and complications could also include unexplained seizures, kidney disease or heart disease. Some may experience one set of signs and symptoms while others experience a completely different set.

"In a young person who should otherwise be healthy, and you even think it could be lupus, that's when you start your laboratory confirmation," says Dr. Susan Manzi, chair of the Allegheny Health Network Medicine Institute, director of the AHN Lupus Center of Excellence in Pittsburgh and board chair of the Lupus Foundation of America.

[See: 6 Signs You're Having a Heart Attack.]

Types of Testing

As with any newly appearing condition, diagnosis starts with a careful medical history, followed by a comprehensive physical examination to turn up suggestive signs. If autoimmune disorders -- such as thyroid disease, rheumatoid arthritis or Type 1 diabetes -- run in your family, that's a lupus risk factor.

If lupus is on the radar, rheumatologists and other specialists use test results like these to help put the pieces together.

Routine Blood Tests

These are common laboratory tests that your primary care provider may order during a regular checkup or to uncover causes of unexplained symptoms:

-- Complete blood count. A CBC measures your red blood cells, white blood cells, platelets and hemoglobin (a protein in red blood cells). Anemia, or reduced levels of healthy red blood cells, is a sign of lupus. Levels of white blood cells, which help fight infection, are often low with lupus.

-- Erythrocyte sedimentation rate. The ESR test measures how quickly red blood cells drop and settle to the bottom of a special test tube. An increased rate is an indication of inflammation somewhere in the body.

-- C-reactive protein. An elevated level of CRP in the blood is a sign of inflammation from an acute infection or a chronic medical condition, like lupus.

-- Thyroid tests. Thyroid-stimulating hormone and thyroid hormone levels can be abnormal in people with autoimmune thyroid disease, a potential lupus complication.

-- Kidney function tests. Creatinine blood tests and blood urea nitrogen levels may indicate changes in your kidneys' ability to filter waste and possible kidney damage. Lupus can attack your kidneys, causing them to fail in some cases.

Urine Tests

Your kidneys remove waste from your body. Because lupus can attack your kidneys, these urine tests can be used to determine if kidney function is impacted:

-- Urinalysis. A single urine sample can reveal problems with kidney function. Certain cell fragments or protein in the urine indicate waste-filtering problems.

-- 24-hour urine sample. If your urine contains excessive protein, you may undergo this additional test to monitor kidney inflammation, or nephritis.

When specialists collaborating from a variety of health disciplines suspect you have an autoimmune condition, they'll order additional bloodwork and other types of testing.

Specialized Testing

"Sometimes you'll see swollen lymph nodes that are enlarged because the immune system is so active attacking cells," Manzi says. In such cases, she says, bloodwork can identify markers of inflammation and auto-antibodies, which may in some cases point to lupus.

Specialized blood testing can include the following:

-- Antinuclear antibody test. ANA is an antibody that attacks your body's own cells. Almost everyone with lupus has a positive ANA test. However, ANA is used to screen for the possibility of lupus rather than as a conclusive diagnostic test. Millions of healthy people who don't have lupus do have this antibody, Manzi notes.

-- Auto-antibody panel. This comprehensive blood test checks for a variety of auto-antibodies related to auto-immune conditions.

Imaging

Imaging tests may be used when people with lupus (diagnosed or not) come to the hospital with acute problems such as chest pain or difficulty breathing. Imaging can also help doctors distinguish lupus complications from those of other diseases, although it's not always necessary.

Doctors may suggest the following imaging tests depending on your individual symptoms:

-- Chest X-ray or CT scans. Standard X-rays or 3D images from CT scans may help reveal underlying causes of symptoms involving organs such as your kidneys, heart or lungs.

-- Joint X-ray. With swollen, painful joints, an X-ray of the hip, knee or shoulder may differentiate lupus from rheumatoid arthritis.

-- Echocardiogram. This noninvasive heart test uses sound waves to reveal heart valve problems or other issues.

-- MRI. This noninvasive test, which creates images using magnetic fields and radio waves, can help determine whether lupus is affecting the central nervous system -- the brain and spinal cord.

Biopsy

A biopsy is a procedure to remove a tissue sample from your body for analysis in a laboratory. You may undergo one of these types of biopsy as part of the diagnostic process:

-- Skin biopsy. This can identify characteristic skin changes related to lupus, such as inflammation at specific skin levels and patterns of deposited antibodies.

-- Kidney biopsy. This can identify characteristic kidney changes related to lupus.

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Evidence of Lupus

To reach a systemic lupus erythematosus diagnosis, doctors use a list of measures developed jointly by the American College of Rheumatology and the European League Against Rheumatism. Measures include the presence of a butterfly facial rash, photosensitivity and evidence of blood and immunologic disorders from test results. Information gleaned from testing allows your health care team to see whether you meet these criteria. If you do, you can then discuss appropriate treatment options to decide the right course for you.