Diagnosing Lupus - Understanding the Process

The Symptoms, Blood Tests, and Criteria Used to Diagnose Lupus

female patient talking with a femal physician
What criteria are used to diagnose lupus?. Getty Images

How do doctors make a diagnosis of lupus? You may have heard that the diagnosis can be tricky and often comes after the condition has been present for a lengthy period of time. What are the criteria required for making the diagnosis and why is this often difficult?

Lupus - The Basics

Lupus, or systemic lupus erythematosis is an autoimmune condition which may include a wide variety of symptoms. It occurs more commonly in women than men, and is often diagnosed between the ages of 15 and 45.

Many people have symptoms for an extended period of time before the diagnosis is made or a misdiagnosis is corrected.

There are five major subtypes of lupus including:

  • Systemic lupus erythematosis
  • Discoid lupus erythematosis
  • Subacute cutaneous lupus erythematosis
  • Drug induced lupus
  • Neonatal lupus

Making the Diagnosis of Lupus - Why is it Difficult?

Making a diagnosis of lupus can be difficult for several reasons. Since this can be so frustrating for people, it might be helpful to list some of these reasons:

  • The symptoms come and go. Lupus is referred to as a relapsing-remitting condition. At times people may have severe symptoms including rashes, painful and swollen joints, and fevers, an at other times may seem quite healthy. Until a pattern is recognized, the disease often goes undiagnosed. Lupus tends to be a very unpredictable condition.
  • There is not a single blood test that can be used alone to make the diagnosis.
  • Lupus is not one disease, but rather there are several subtypes.
  • Even with the same subtypes, lupus is a "snowflake." What that means is that no two people with lupus have identical symptoms.
  • Lupus can mimic many other connective tissue disorders as well as other medical conditions. For example, people with lupus may be misdiagnosed as having multiple sclerosis.
  • Lupus is relatively uncommon. Though lupus is not rare, primary care physicians may miss the diagnosis because they have not seen a patient with lupus before.

Criteria for Diagnosing Lupus

In order to make the diagnosis of lupus a little clearer, the Amercian College of Rheumatology has devised a criteria list. This list includes symptoms that raise suspicion that the condition is present, but with blood tests used to confirm the diagnosis as the gold standard.

To better understand what these criteria may include, let's first look at the common signs and symptoms of the disease as well as some of the blood tests which are done.

Common Signs and Symptoms of Lupus

As noted above, the signs and symptoms of lupus are different for everyone.The most common symptoms overall include swollen joints, a fever, and fatigue. A rash is also very common including the characteristic rash on the nose and cheeks known as a butterfly or malar rash. Other common symptoms include hair loss, muscle pain, fingers or toes which become purple in the cold (Raynaud's phenomenon,) sun sensitivity (photosensitivity,) facial swelling, mouth ulcers, and anemia.

Systemic lupus also affects different organs and organ systems.

Those most commonly affected include the:

  • Kidneys (lupus nephritis.)
  • Lungs (lupus related pleurisy.)
  • Central nervous system, leading to headaches, confusion, and seizures. The risk of stroke is increased as well. (Learn more about lupus and the nervous system.)
  • Blood vessels (vasculitis.)
  • Heart (lupus pericarditis and lupus myocarditits.)
  • Bone marrow - Lupus may affect all of the blood cells in the bone marrow resulting in anemia (due to a reduced level of red blood cells,) leukpenia (a low level of white blood cells which may increase the risk of infection,) and thrombocytopenia (a low level of platelets which can lead to bleeding and bruising.)

    Blood Tests Used in Diagnosing Lupus

    There are a number of blood tests which are evaluated in the process of diagnosing lupus.

    Anti-Nuclear Antibodies

    The first test which is done when the diagnosis of lupus is considered is an anti-nuclear antibody blood test (ANA.) This test identifies the presence of autoantibodies—antibodies which attack the body's own tissues and cells.

    There are several steps involved in looking at the ANA. In addition to reporting whether it is positive or negative, the lab will also report the titer (a measure of the number of autoantibodies present,)  and the pattern, whether homogeneous, peripheral, speckled, or nucleolar. With lupus, a homogeneous pattern is seen most often, followed by a peripheral pattern.

    A positive ANA does not automatically mean a person has lupus. The presence of a positive ANA could indicate the presence of another connective tissue disease or a wide variety of other conditions. A positive ANA is also found in around five percent of healthy adults. That said, roughly 95 percent of people with lupus will have a positive ANA.

    Additional Antibodies

    If a person has a positive ANA, a number of other tests will be ordered to understand what particular antibody is responsible for the ANA test. Three specific tests in particular will be tested:

    • Anti-dsDNA (anti-double stranded DNA)
    • Anti-Sm (anti-Smith antibodies)
    • Anti-RNP (anti-ribonucleoprotein antibodies)

    Anti-dsDNA and anti-RNP tests confirm whether antibodies are being produced to attack the genetic material (the DNA) in the cell. The anti-Sm test measures whether there are antibodies against a certain protein found in the nucleus of cells. Anti-dsDNA is positive in roughly 50 percent of people with lupus, while 30 to 40 percent are positive for anti-Sm.

    The combination of a positive ANA, anti-double stranded DNA and anti-Smith antibodies is usually considered the "gold standard" in making the diagnosis of lupus.

    Anti-RNP antibodies are those which attack the ribonucleoproteins responsible for many chemical activities in cells, and usually indicates some form of connective tissue disease is present.
    There are several other antibodies which may be found, include antibodies to phospholipids (anti-phospholipid antibodies or the "lupus anticoagulant",) and antibodies to histone.

    American College of Rheumatology Criteria for a Lupus (SLE) Diagnosis - Putting Symptoms, Signs, and Blood Tests Together

    Lupus (systemic lupus) is differentiated from other connective tissue diseases, based on eleven criteria offered by the American College of Rheumatology for classification purposes. These include:

    • A butterfly-shaped (malar) rash across the cheeks and nose.
    • A scaly disk-shaped (discoid) rash which appears red and raised on the face, neck, ears, scalp, or chest.
    • Sunlight sensitivity (photosensitivity.)
    • Mouth and/or nose sores (ulcers) sores.
    • Arthritis (nonerosive) in two or more joints when combined with pain, swelling, or an effusion. (Unlike erosive arthritis, the inflammation associated with lupus does not destroy the joints.)
    • Heart and/or lung involvement such as pleurisy or pericarditis.
    • Kidney problems including protein in the urine (proteinuria) or cellular casts in the urine.
    • Neurologic problems such as headaches, seizures, or psychosis.
    • Blood problems such as a low level of red blood cells (anemia,) white blood cells (leukopenia,) or platelets (thrombocytopenia.)
    • Immune system malfunction due to autoantibodies.
    • Antinuclear antibodies - A positive ANA unless a person is on a medication known to cause a positive ANA. (Keep in mind that a positive ANA may be found with many other conditions as well as in healthy normal individuals.)

    Could You Have Lupus?

    While doctors often look at the criteria above in confirming a diagnosis, other tools can help people get an idea if they might have the condition. If your answer is "yes" to three more more of the questions on this criteria list, or are concerned after taking our quiz, "Could You Have Lupus?" talk to your doctor.

    If you aren't getting answers, consider getting a second opinion, and learn about what types of doctors care for people with lupus.

    Sources:

    American College of Rheumatology. Lupus. 2017. https://www.rheumatology.org/I-Am-A/Patient-Caregiver/Diseases-Conditions/Lupus

    Kasper, Dennis L.., Anthony S. Fauci, and Stephen L.. Hauser. Harrison's Principles of Internal Medicine. New York: Mc Graw Hill education, 2015. Print.

    Lam, N., Ghetu, M., and M. Bieniek. Systemic Lupus Erythematosis: Primary Care Approach to Diagnosis and Management. American Family Physician. 2016. 94(4):284-94.

    Continue Reading