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University of Iowa Diagnostic Laboratories (UIDL) Test Directory 319-384-7212 (local) 1-866-844-2522 (toll free) |
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| RNP/SM Antibody (ENA) | Order Code: RNPSM
Order Form: Immunopathology Requisition |
Specimen: |
Serum | ||
Collection Medium: |
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Minimum: |
Adult - 5 ml; red top tube Pediatric - 2 ml; red top tube | ||
Testing Schedule: |
Testing performed once a week. | ||
Analytic Time: |
1 week | ||
Reference Range: |
Negative = < 20 units Weak positive = 20-39 units Moderate positive = 40-80 units Strong positive = > 80 units | ||
Comments: |
When indirect immunofluorescence test for ANA is positive, the tests for anti-Sm and anti-RNP are helpful in differential diagnoses of various rheumatic diseases. The specificity of the anti-RNP detected is for U-1-RNP (U1-RNP). Testing performed once a week. These two tests are most informative when ordered together in the initial evaluation of patients for autoimmune connective tissue diseases. Anti-Sm is a specific marker antibody for systemic lupus erythematosus (SLE) but is positive in only about one-third of cases. Anti-RNP will also be positive whenever anti-Sm is detected, but can be detected in some SLE patients in the absence of anti-Sm. Anti-RNP may also be found in several other autoimmune connective tissue diseases, however. It is particularly associated with mixed connective tissue disease in which very high levels of anti-RNP are present. The tests are listed together as "anti-RNP/SM" on the current Immunopathology Laboratory requisition. If this box is checked, then both EIA assays will be performed and two charges will be generated. | ||
Methodology: |
Enzyme Linked Immunosorbent Assay (ELISA) | ||
Sample Processing: |
Centrifuge at 3500 RPM for 5 minutes. Aliquot serum into labeled container and cap. | ||
Sample Storage: |
Refrigerate serum 2-8 degree C. | ||
Transport Instructions: |
Place specimen into zip-lock type bag, seal bag. Place requisition into outside pocket of bag. Ship at ambient temperature. |
Updated: 01/10/2008