Diagnosing systemic lupus erythematosus is as complex as the disease itself
Diagnosing the chronic autoimmune disease systemic lupus erythematosus (SLE) is complex. Symptoms vary according to which tissues are attacked, and are common enough to be attributed to many other conditions. Its incidence also alters according to ethnicity and gender. Where do you start?
Dr Daman Langguth, Clinical Immunologist and Immunopathologist at Sullivan Nicolaides Pathology, said there isn’t one pathology test that confirms a diagnosis of SLE. If it is suspected then an antinuclear antibody (ANA) test is usually the first pathology investigation requested. This test doesn’t confirm the diagnosis. It flags that an autoimmune disease may be present. Most people with a positive ANA do not have an autoimmune disease.
“If the ANA test is positive then subsequent pathology investigations might include an anti-double stranded DNA test (anti-dsDNA) that specifically targets the genetic material found in the nucleus of cells, an ENA (Extractable Nuclear Antigen Antibodies) Panel, and a test for complement proteins,” he explained.
An ENA Panel detects the presence of one or more specific autoantibodies in the blood and the resulting pattern of positive and negative results helps diagnose different autoimmune disorders. Complement proteins are a part of the immune system, and their levels can be used to help diagnosis or monitor disease activity. Presenting symptoms are also investigated, including investigating which organs, tissues and joints are affected.
“SLE is a true protean multisystem disorder. It can affect every organ except the liver, and we don’t know why this is the case. It can also affect the skin, eyes and joints, and cause diseases such as pleurisy and pancreatitis. Between 10 and 30% of patients have kidney involvement and this is called lupus nephritis. If this is suspected, then pathology tests may be requested to check the kidneys’ function,” said Dr Langguth.
SLE can affect anyone at any age, but it has a known risk profile. About nine in 10 people affected are pre-menopausal women, mostly between 15 and 45 years of age. Post menopause the incidence becomes equal for men and women.
“The male and female disease profile is also different. Men usually experience sudden severe episodes while women tend to have it simmering in the background all of the time,” explained Dr Langguth.
He also said a person’s ethnicity is also a risk factor.
“African Americans have the highest risk with an incidence of one in 70. But people of African ethnicity don’t have a high incidence if they reside in Africa. This is because of the genetic relationship between cerebral malaria and SLE. The genes that protect people from this type of malaria also promote developing SLE. When people of African ethnicity live in a malaria-free country such as North America, their incidence of SLE increases.”
Other ethnicities at greater risk are non-Caucasian populations such as Aboriginals, Hispanics/Latinos, Asians, Native Americans, Native Hawaiians and Pacific Islanders. It is also more prevalent in some families.
Dr Langguth said SLE is still relatively poorly understood but responsible for a significant degree of disability in the community. It is also a disease for life. Early diagnosis can prevent serious downstream complications, but that’s not as simple as it sounds. It takes about seven years from onset of disease to measureable symptoms, and there is no single pathology test for it. That’s part of the reason why diagnosing SLE is often as complex as the disease itself.
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This article appeared in the October 2017 Edition of ePathWay which is an online magazine produced by the Royal College of Pathologists of Australasia (http://www.rcpa.edu.au/Library/Publications/ePathway).
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