If your symptoms suggest SLE then your doctor will do some blood tests to diagnose SLE. Read about various blood and urine tests conducted to diagnose lupus.
The symptoms of Systematic Lupus can be vague, making it difficult to diagnose. Even when they do, patients can have a wide variety of organ involvement to make it difficult for a single test to detect it.
American Rheumatism Association has drawn 11 criteria based on various symptoms of SLE, to help doctors improve the accuracy of its diagnosis. A person is strongly thought to be suffering from SLE, if they develop at least 4 of these symptoms.
- A “butterfly rash” over the cheeks of patients face referred to as malar rash.
- Patchy redness with hyperpigmentation and hypopigmentation that can cause scarring.
- Skin rash in reaction to ultraviolate sunrays.
- Spontaneous sores or ulcers on the lining of mouth, nose or throat.
- Two or more swollen, tender joints of the extremities; also known as arthritis.
- Inflammation of the lining tissue around the heart or lungs, usually associated with chest pain upon breathing or changes of body position.
- Abnormal amounts of urine protein or clumps of cellular elements called casts that are detectable with a urinalysis.
- Brain irritation manifested by seizures and/or psychosis.
- Low white blood count (WBC) or red blood count (RBC), or platelet count on routine complete blood count testing.
- Abnormal immune tests include anti-DNA or anti-Sm [Smith] antibodies, falsely positive blood test for syphilis, anticardiolipin antibodies, lupus anticoagulant, or positive LE prep test.
- Positive testing of antinuclear antibodies in the blood.
With proper clinical criteria, some tests can help confirm a diagnosis of lupus. They can also help monitor the disease and show the effects of treatment.
Antinuclear Antibody (ANA) Test
Everyone with active lupus contains ANA which acts as a screening tool. Distinct antibody patterns can help doctors detect specific disease. However, a positive result for this test may not necessarily indicate lupus. Positive results are often seen with some other diseases and in a smaller percentage of people without lupus or other autoimmune disorders. This is why, doctors must consider testing the patient for other criteria also.
Antiphospholipid Antibodies (APLs) Test
Up to 60% of people with lupus contain APLs. Their presence can help confirm a diagnosis. But, people without lupus may also have APLs, making them not a foolproof method to detect lupus.
Anti-Sm is an antibody directed against Sm, a specific protein found in the cell nucleus. Up to 30% of people with lupus have the protein Sm and found rarely in people without it. This is why, a positive result to this test helps confirm lupus. But the test gets limited for the fact that only 30% of people with lupus test positive for the test. It can miss a large majority of people with lupus.
Besides blood tests, certain urine tests can also be used to diagnose and monitor the effects of lupus on kidneys. They are:
Measurement of Glomerular Filtration Rate and Proteinuria
This test measures how effective the kidneys are at filtering the blood to eliminate waste products. It is conducted on urine collected over a 24-hour period.
This test is performed on a one-time urine sample. It measures for protein loss, which is an indicator of kidney function.
Urinalysis can be used in screening for kidney disease. The presence of protein, red blood cells, white blood cells, and cellular casts may all indicate kidney disease.
Once SLE is diagnosed, you will normally be advised to have regular checks and tests. For example, regular blood tests to check for anaemia and urine tests to check for kidney problems.
Read more articles on Lupus.
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