How is lupus diagnosis made?
Sometimes, diagnosis of lupus is fairly straightforward when someone has multiple manifestations of the disease (see “Systemic Lupus Erythematosus: What is it?“). Too often, the lupus diagnosis is difficult as symptoms may be vague and nonspecific, and tests may be inconclusive. A rheumatologist is an expert in the field of autoimmune diseases which can make the diagnosis by putting together all the data from the history, physical exam, labs, or imaging studies. It is much like trying to solve a Jigsaw puzzle: you’d like to have as many pieces as possible, but often many pieces are still missing. It takes a trained eye to discover the full picture.
Lupus is a disease that can affect about every organ. Therefore, when evaluating someone for lupus, I ask questions that cover these symptoms- Are there any rashes (skin), ulcers in the mouth or nose (mucous membrane), chest pain or shortness of breath (heart, lungs), etc. Past history is also important as symptoms in the past may also provide some clues. Does anyone in the family has any autoimmune diseases? Genetic can play a role. What medications are you on? Some medications can actually cause lupus. What is your occupation? Are there any environmental risk factors? Is there a history of miscarriages? The list goes on!
They physical exam
The next step in evaluation for lupus is a very thorough physical examination, looking for the signs of the disease- like hair thinning, rashes, ulcers in the mouth, joint inflammation, etc.
Several labs can be abnormal in lupus, including:
- Positive anti-nuclear antibody (ANA), andi-double stranded DNA antibody (dsDNA), anti-smith antibody, anti-RNP antibody, anti-phospholipid antibodies
- Low blood cell counts: low white cells (leukopenia), red cells (anemia), or platelets (thrombocytopenia)
- Low complement levels C3, C4. These are parts of the immune system that often depress during a lupus flare
- Elevated inflammatory markers (ESR, CRP)
- Abnormal kidney function
- Presence of blood or protein in the urine
Imaging studies are not always needed, but when the diagnosis is unclear, they may provide a clue
- Xrays of the tender or swollen joints
- Echocardiogram (ultrasound of the heart) to look for fluid around the heart, assess valve function, etc.
- Chest xray to evaluate the lungs
- Ultrasound of the kidneys
- Cat scan (CT) of the lungs or abdomen
- MRI of the brain
- Angiogram to rule out vasculitis
Biopsy of the affected organ (like skin, lungs, kidneys, etc) can be used to confirm the diagnosis and rule out other diseases
- Lumbar puncture, to get a sample of the spinal fluid, can be used to evaluate for presence of lupus in the brain.
Lupus diagnostic criteria
Since lupus can affect any organ in the body, and since many of the symptoms are nonspecific, most rheumatologists use the 1997 diagnostic criteria from the American College of Rheumatology (ACR). This criteria include 11 signs and symptoms thought to be fairly specific for lupus. Presence of 4 criteria is required to meet the classification.
- Malar rash- red “butterfly rash” over the cheeks and nose
- Discoid rash- raised patches of skin that can scar
- Photosensitivity rash- rash that occurs with exposure to sunlight
- Ulcers- in the mouth or nose
- Arthritis- tenderness and swelling in joints
- Serositis- fluid in the lining around the lungs (pleuritis) or the heart (pericarditis)
- Kidney disease- presence of too much protein or blood in the urine
- Blood disorder- low white cells (leukopenia), red cells (anemia), or platelets (thrombocytopenia)
- Positive ANA
- Other antibodies- anti-double stranded DNA, anti-Smith antibodies, or antiphospholipid antibodies
How good is the diagnostic criteria?
It’s pretty good, but it’s not perfect. Some people with lupus may not fulfill the criteria- for example, lupus can be diagnosed on kidney biopsy even if the other criteria are not present. Also, less frequently, people who fulfill the criteria may not have lupus. Each of the criteria can be seen with other diseases. For example, mouth ulcers can also happen in Crohn’s disease; Rosacea can look just like malar rash, cancer of the bone marrow can cause low white cells, red cells, platelets, etc. A real detective- ie a rheumatologist- may be needed to figure out the diagnosis!