Section: Veterinary Care In-depth
Diagnosis In-depth
A definitive diagnosis of systemic lupus erythematosus requires two major signs accompanied by a positive ANA test or one major and two minor signs accompanied by a positive ANA test. A probable diagnosis requires one major or two minor signs with a negative ANA test.
Major Signs
Arthritis involving multiple joints that does not erode the cartilage
Muscle inflammation
Skin inflammation involving blisters
Increased protein levels in the urine
Other concurrent immune diseases such as immune mediated hemolytic anemia (low red blood cells), thrombocytopenia (low platelets) and leukopenia (low white blood cells)
Minor Signs
Fever
Mouth ulcers
Inflammation of the lining of the chest cavity
Inflammation of the heart muscle or sac surrounding the heart
Enlarged lymph nodes
Dementia
Seizures
Other Tests
A complete blood count (CBC) may show anemia, low platelet count and low or high white blood cell count. If a regenerative anemia (one that shows evidence of response on the part of the bone marrow) is present without evidence of blood loss and with or without clumping of red blood cells on the slide (autoagglutination), a direct Coomb's test is recommended to identify destruction of red blood cells by auto-antibodies. If anemia is non-regenerative, collection and microscopic evaluation of a bone marrow sample is recommended.
Results of serum biochemistry tests are often non-specific. A high blood globulin concentration may be observed as a manifestation of the inflammatory response. The presence of low serum albumin concentration and high cholesterol concentration may signal the presence of kidney disease characterized by damage to the microscopic filters of the kidney (glomerulonephritis).
Urinalysis may show proteinuria as a consequence of glomerulonephritis. Normal urinalysis results do not rule out the possibility of systemic lupus erythematosus.
Collection of joint fluid for microscopic analysis may show large numbers of white blood cells called neutrophils, absence of bacteria and moderate numbers of white blood cells called mononuclear cells.
The antinuclear antibody test (ANA) is considered the most sensitive and specific test to aid in the diagnosis of systemic lupus erythematosus. It is positive in up to 90 percent of cases, so a negative ANA does not always rule out the possibility of lupus. In dogs, there is no correlation between the amount of antinuclear antibodies present and the severity or course of the disease. Glucocorticoid therapy may cause false negative results on the antinuclear antibody test. False positive results may occur in dogs with cancer, chronic skin disease, or chronic bacterial infection.
The LE cell preparation is not as specific as the ANA test and is more commonly affected (rendered negative) by glucocorticoid treatment. This test detects the presence of white blood cells that have engulfed other cell nuclei that have been coated with auto-antibodies.
The microscopic pathology findings in skin biopsy specimens are characteristic of systemic lupus erythematosus and may be helpful in the diagnosis of this disease.
An immunofluorescence test to detect antibody deposition in tissues may show the presence of auto-antibodies of the types called immunoglobulin M (IgM) and immunoglobulin A (IgA). Another inflammatory protein component called complement (C3) also may be detected. This test may be positive in 50 to 90 percent of dogs with systemic lupus erythematosus.
Skin samples from the nose or footpads of normal dogs may show positive immunofluorescence results. Thus, these sites should be avoided when the immunofluorescence test is done. Treatment with glucocorticoids may cause false negative results.
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