Last updated Feb. 2, 2023, by Marisa Wexler, MS
Fact-checked by Patricia Silva, PhD
Lupus is an autoimmune disorder wherein the immune system attacks the body’s own healthy tissue. A diagnosis can be challenging as there is no single, definite test available. Furthermore, lupus symptoms can present differently among patients and show overlap with other disorders, complicating diagnosing the disease.
What are the criteria for diagnosing lupus?
Formal criteria for classifying systemic lupus erythematosus (SLE), the most common and serious type of lupus, were first published by the American College of Rheumatology (ACR) in 1982. The criteria have since been updated numerous times as the understanding of lupus has evolved. The most recent criteria were published in 2019 by the ACR and the European League Against Rheumatism (EULAR).
Under the 2019 criteria, positive testing for antinuclear autoantibodies (ANAs) is a required criterion. In other words, a person can only be diagnosed with lupus if they test positive for ANAs at least once. ANAs are made by immune B-cells that play a role in the autoimmune attack that causes lupus.
Many people who are positive for ANAs do not have lupus, so additional testing is required.
In patients who are positive for ANAs, a diagnostic workup for lupus involves looking for signs of disease involvement across seven types of symptoms, namely:
- constitutional (whole-body) symptoms, most notably fever
- blood-related symptoms (hematological), such as low counts of white blood cells and platelets
- neuropsychiatric symptoms, like seizure or psychosis
- skin-related symptoms, including rash (namely a butterfly-shaped rash over the cheeks, referred to as malar rash), hair loss, and mouth ulcers
- musculoskeletal symptoms, such as joint pain and other forms of muscle and bone involvement
- kidney dysfunction
- symptoms affecting membranes (tissue lining) in the body, including those around the heart and lungs which can cause chest pain
A diagnostic workup for lupus will also involve tests for three other characteristic signs of disease-driving autoimmunity:
- antibodies that attack the membranes of cells called antiphospholipid antibodies
- antibodies against Smith (anti-Sm) and double-stranded DNA (anti-dsDNA), which are highly specific for lupus
- abnormal levels of proteins part of the complement system, the front line defense of the immune system
Based on the combination of symptoms and immunological findings, the 2019 criteria outline a system that can be used to assign a numeric score to those who are ANA-positive. If the score is 10 or higher, the person is classified as having lupus.
The term “borderline lupus” is sometimes used to describe people who have some signs and symptoms of lupus-like disease, but where there isn’t enough information to fulfill the formal diagnostic criteria.
For example, some people may test positive for ANAs but have no substantial symptoms to facilitate a diagnosis, or other co-occurring issues may cause confusion about whether symptoms are attributable to lupus autoimmunity.
Some people with “borderline lupus” will eventually develop additional signs and symptoms to the point that they can be formally diagnosed with the disease. Studies estimate that this occurs in anywhere from 10-50% of cases, usually within the first few years after the onset of symptoms.
What tests can be used to diagnose lupus?
There is no single test that can diagnose lupus. Diagnostic workup for the disease involves detailed exams and looking at a patient history to assess whether a person is having symptoms indicative of lupus, and to rule out other potential explanations for those symptoms. Diagnosing lupus also involves laboratory tests to look for characteristic signs of autoimmunity and organ dysfunction.
Blood analysis is one of the main tools used to help diagnose lupus. It’s used to identify ANAs and other markers of the autoimmune attack characteristic of the disease. Blood tests can also help identify signs of the disease, such as low blood cell counts and abnormal clotting activity.
Lupus can cause inflammation that damages the kidneys, a condition referred to as lupus nephritis, which is one of the most common serious complications of the disease. Urine tests can be used to assess kidney function. These tests check urine for high levels of cell debris and protein, which are usually filtered out of the urine when the kidneys are working properly.
A biopsy involves taking a small piece of tissue to be analyzed in a laboratory. Biopsy of the kidney or skin is common in the diagnostic evaluation of lupus, as this can help identify characteristic forms of tissue damage and inflammation caused by the autoimmune attack that drives the disease.
Lupus News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.