If the first time you heard of lupus was during a recent episode of Keeping Up With The Kardashians, you’re not alone. The condition affects only about 20,000 people in Australia and New Zealand1.
According to news delivered on the show earlier this month, Kim Kardashian West’s blood had tested positive for “lupus and rheumatoid arthritis antibodies”. However, a subsequent episode revealed that her symptoms of tiredness and swollen hands were actually due to psoriatic arthritis.
So, what are these autoimmune conditions and why the confusion?
Systemic Lupus Erythematosus usually known as lupus or SLE is a condition that affects more women than men – eight times more in fact.2 It is a chronic, inflammatory autoimmune disorder that can affect several organ systems including the kidneys, skin, joints and other internal organs.
Lupus usually begins in one organ but can progress to involve others. Possible symptoms that may be experienced include: joint pain; fatigue, headaches and a skin rash – which often manifests in a butterfly shape across the nose and cheeks. In rare cases serious symptoms can occur such as seizures, psychoses, inflammation in the heart and lungs, and blood clots that could lead to a stroke or pulmonary embolism.
Rheumatoid arthritis is a chronic autoimmune condition affecting around 450,000 Australians.3 It affects the joints when your immune system malfunctions and attacks healthy tissue in or near your joints. Common symptoms include swelling, pain and heat in the joints, joint stiffness and persistent fatigue.
Psoriatic arthritis causes inflammation of the joints which can result in pain, swelling and stiffness in the joints, pain in tendons and thickening or colour changes in the nails. It affects people who have psoriasis and but only between 10 and 30 percent of people with psoriasis will develop this type of arthritis.
What did Kim’s ‘positive’ lupus result mean?
Diagnosing autoimmune conditions like lupus can be complex. Immunopathologist Associate Professor Stephen Adelstein explains:
“People sometimes think that a test alone can diagnose a disease, but it can’t. We must look at a patient’s symptoms, a comprehensive medical and family history, as well as pathology results to understand what is causing the problem.
Results from a range of tests are often needed to reach a diagnosis, particularly when symptoms are similar across several conditions.”
The pathology tests we have available for autoimmune conditions look for clues in the blood that tell us about certain body processes that are happening.
For example, the antinuclear antibody (ANA) test is often ordered by doctors if they suspect lupus. ANAs are a group of special antibodies produced by the patient’s immune system when it malfunctions and cannot tell the difference between ‘self’ and ‘other’. They are known as autoantibodies and can attack the body’s own cells, causing symptoms such as tissue and organ inflammation, joint and muscle pain, and fatigue.
Detecting ANA in the blood shows that an autoimmune process is taking place. The ANA test is most commonly used to indicate lupus but is also associated with other autoimmune disorders. However, a positive result can happen in some people without an autoimmune condition and this is more common as we age, with 30% of women and 20% of men being ANA positive by age 70.4
In pathology this is known as a test that is highly sensitive but not highly specific. This means the test is able to pick up close to 100 per cent of people who have the autoantibodies in their blood, but cannot specify that they have lupus, because someone who does not have lupus may still have a positive result.
For this reason, after a positive ANA result, doctors will often order an Anti-dsDNA test that is a more specific test to confirm a lupus diagnosis. We don’t know what tests were ordered in Kim’s specific case, but it certainly highlights the complexities of diagnosing autoimmune diseases.
A/Prof Adelstein says; “This is a constantly evolving area. We are always looking for ways to improve the diagnostic ability of the tests we have and to develop new tests that can be more specific and more sensitive so that patients can be diagnosed and treated more quickly.”