Diagnosing lupus is complicated due to the fact that signs and symptoms differ considerably from one person to another. Signs and symptoms of lupus may vary over time and overlap with those of several other illnesses. No single test can diagnose lupus. The combination of blood and urine tests, indications and symptoms, and physical examination findings leads to the diagnosis.
A complete blood count measures the number of red blood cells, white blood cells and platelets as well as the amount of hemoglobin and protein in red blood cells. Results may show you have anemia, which is very common in patients with SLE. Decreased white blood cell or platelet count may also show in lupus patients.
Erythrocyte Sedimentation Rate (ESR)
An erythrocyte sedimentation rate or ESR is a test for lupus that tells the rate at which red blood cells settle to the bottom of a tube in an hour. A person with systemic disease, such as lupus may show an increased rate than the normal. However, the sedimentation rate is non-specific for any one disease. It may be elevated if you have lupus, another inflammatory condition, cancer or an infection. Kidney and liver assessment involve blood tests which can evaluate how well your kidneys and liver are functioning. Lupus can affect these organs. High protein level or red blood cells in the urine is reflected in the urinalysis, which may occur if lupus has affected your kidneys.
Antinuclear Antibody (ANA) & Anti-extractable Nuclear Antigen (Anti-ENA)
Tests for lupus may also include antinuclear antibody (ANA) testing and anti-extractable nuclear antigen (anti-ENA) which form the bastion of serologic type tests for lupus. Different methods are used to detect ANAs. The most extensively used method, clinically, is indirect immunofluorescence. The pattern of fluorescence suggests the kind of antibody present in the serum of the patient.
ANA screening produces positive results in several connective tissue disorders and other autoimmune diseases, and may manifest in normal individuals. Subtypes of antinuclear antibodies include anti-Smith and anti-double stranded DNA (dsDNA) antibodies (which are traced to Systemic Lupus Erythematosus or SLE) and anti-histone antibodies (which are linked to drug-induced lupus). Anti-dsDNA antibodies are highly specific for SLE and are present in 70 percent of cases but appear in only 0.5 percent of people without SLE according to Wikipedia. The anti-dsDNA antibody titers also tend to suggest disease activity, although not in all cases.
Routine Tests for Lupus
Other routinely formed tests for lupus suspected to be inflicted by an individual are complement system levels (low levels suggest consumption by the immune system), electrolytes and renal function (disturbed if the kidney is involved), liver enzymes, and complete blood count.
Lupus Erythematosus (LE) Cell Test
The lupus erythematosus (LE) cell test was commonly used for diagnosis, but it is no longer practiced because the LE cells are only found in 50 to 75 percent of SLE cases, and they are also found in some people with rheumatoid arthritis, scleroderma, and drug sensitivities. The LE cell test is now performed only rarely and is mostly of historical significance due to this instance.