Diagnosing systemic lupus erythematosus, better known simply as lupus, can be a difficult task, as symptoms can come and go and be either mild or severe. Patterns can be tricky to map, and some people may suffer for months or years before a diagnosis is made.
When diagnosing the disease, doctors take in many factors, including a patient’s medical history, routine lab test results, and specialized tests focused on immune status. These tests can be used as much to rule out lupus as to indicate the disease. Since lupus is a systemic (body-wide) disease, doctors also look for symptoms in more than one of the body’s systems -- such as the kidneys and the skin.
Doctors are tasked with interpreting test results, then correlating them with symptoms and other test results. It is difficult when patients exhibit vague symptoms and clashing test results. Skillful doctors can put the pieces of the puzzle together and determine whether a person has lupus or something else entirely.
Here is a list of some of these diagnostic tests -- many of them screening tests, or tests that help healthcare practitioners use in conjunction with other tests to help piece together the puzzle -- along with a short description of each:
Complete Blood Count (CBC):
The complete blood count (CBC) screening test has many applications, and it can help identify a wide variety of diseases.
In it’s simplest definition, the CBC is used to measure red blood cell and white blood cell count, total amount of hemoglobin in the blood, hematocrit (the amount of blood composed of red blood cells) and mean corpuscular volume (the size of red blood cells). In fact, the CBC can count additional blood cell types like neutrophils, eosinophils, basophils, lymphocytes, monocytes, and platelets.
Results from the CBC can help detect problems such as dehydration or loss of blood, abnormalities in blood cell production and life span, as well as acute or chronic infection, allergies, and problems with clotting.
Erythrocyte Sedimentation Rate:
The erythrocyte sedimentation rate (ESR) test measures inflammation in the body and is used to help diagnose conditions associated with acute and chronic inflammation, including lupus. It is usually used in conjunction with other tests, as the test itself is nonspecific. In other words, it can detect increases in inflammation, but it does not pinpoint where the inflammation is or point to a specific disease. Other conditions can affect outcomes of the test, as well. The test is one that is usually conducted several times over a certain time period to measure changes in inflammation.
Changes in ESR over time can help guide a healthcare professional toward a possible diagnosis.
- Moderately elevated ESR occurs with inflammation, but also with anemia, infection, pregnancy, and old age.
- A very high ESR usually has an obvious cause, such as a marked increase in globulins that can be due to a severe infection.
- A rising ESR can mean an increase in inflammation or a poor response to a therapy.
- A decreasing ESR can mean a good response (though note that a low ESR can be indicative of diseases such as polycythemia, extreme leukocytosis, and protein abnormalities).
This screening test is used to detect substances or cellular material in the urine associated with metabolic and kidney disorders. It is a routine test, and doctors utilize it to detect abnormalities -- abnormalities that often appear before patients suspect a problem. For those with acute or chronic conditions, regular urinalysis can help monitor organ function, status, and response to treatment.
The complement system is the name of a group of proteins that move through your bloodstream, and complement levels -- as the name implies -- measure the activity of those proteins. Working within the immune system, the proteins play a role in the development of inflammation. The test is often used to monitor patients with lupus and other autoimmune diseases to see if treatment is working. Though it can point to a number of conditions, a decreased complement level can point toward SLE and lupus nephritis.
Antinuclear Antibody Test (ANA):
The antinuclear antibody (ANA) test is used to detect autoantibodies that react against components of the nucleus of the body's cells. While most people with lupus test positive for ANA, medical conditions such as infections, other autoimmune diseases and false positives can also produce a positive test result. For this reason, your doctor may order some other blood tests to correctly diagnose SLE.
Other Autoantibody Tests
Usually in conjunction with the ANA test, your doctor may ask that you take other tests that can help determine the presence of three specific types of antibodies: anti-dsDNA (anti-double-stranded DNA), anti-Sm (anti-Smith antibodies), and anti-RNP antibodies. The anti-dsDNA and anti-RNP tests confirm whether there are antibodies being produced to the genetic material in the cell. The anti-Sm test measures if there are antibodies against a certain protein found in the nucleus of cells. When either the anti-dsDNA or the anti-Sm antibody test is positive, a person is usually considered to have SLE. Knowing which particular antibody is responsible for the positive ANA test can help determine which autoimmune disease is present.
Lupus Anticoagulant Antibody Test
Lupus anticoagulant antibodies react with proteins bound to phospholipid, a type of fat molecule that is part of the normal cell membrane and found in the blood stream. They are also categorized as antiphospholipid antibodies.
These antibodies interfere with the normal function of blood vessels and can lead to narrowing of the blood vessels or blood clots. These complications can lead to stroke, heart attack, and miscarriage.
While lupus anticoagulants are typically discovered in systemic lupus erythematosus patients, they are also known to occur in people with other autoimmune diseases, certain infections, and tumors, as well as in people who take certain medications, including phenothiazines, phenytoin, hydralazine, quinine, amoxicillin, and birth control pills.